Amr lives in Lala Land. Lala Land is a very beautiful country that is located on a coordinate line. Lala Land is famous with its apple trees growing everywhere.

Lala Land has exactly n apple trees. Tree number i is located in a position xi and has ai apples growing on it. Amr wants to collect apples from the apple trees. Amr currently stands in x = 0 position. At the beginning, he can choose whether to go right or left. He'll continue in his direction until he meets an apple tree he didn't visit before. He'll take all of its apples and then reverse his direction, continue walking in this direction until he meets another apple tree he didn't visit before and so on. In the other words, Amr reverses his direction when visiting each new apple tree. Amr will stop collecting apples when there are no more trees he didn't visit in the direction he is facing.

What is the maximum number of apples he can collect?

Input

The first line contains one number n (1 ≤ n ≤ 100), the number of apple trees in Lala Land.

The following n lines contains two integers each xi, ai ( - 105 ≤ xi ≤ 105, xi ≠ 0, 1 ≤ ai ≤ 105), representing the position of the i-th tree and number of apples on it.

It's guaranteed that there is at most one apple tree at each coordinate. It's guaranteed that no tree grows in point 0.

Output

Output the maximum number of apples Amr can collect.

Examples

Input

2
-1 5
1 5


Output

10

Input

3
-2 2
1 4
-1 3


Output

9

Input

3
1 9
3 5
7 10


Output

9

Note

In the first sample test it doesn't matter if Amr chose at first to go left or right. In both cases he'll get all the apples.

In the second sample test the optimal solution is to go left to x = - 1, collect apples from there, then the direction will be reversed, Amr has to go to x = 1, collect apples from there, then the direction will be reversed and Amr goes to the final tree x = - 2.

In the third sample test the optimal solution is to go right to x = 1, collect apples from there, then the direction will be reversed and Amr will not be able to collect anymore apples because there are no apple trees to his left.

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class hrg
{
    static void shuffle( int arr[])
    {
        int n = arr.length;
        Random r = new Random();
         
       for (int i = n-1; i > 0; i--) {
           int j = r.nextInt(i+1);
             
            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
    }
    static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        }
        int[][] tdiarr(int m , int n){
            int[][] a = new int[m][n];
            for(int i=0;i<m;i++){
                for(int j=0;j<n;j++){
                    a[i][j]=Integer.parseInt(next());
                }
            }
            return a;
        } 
        int[] niarr(int n)
        {
            int[] a = new int[n];
            for(int i=0;i<n;i++)a[i]=Integer.parseInt(next());
            return a;
        }
        long[] nlarr(int n)
        {
            long[] a = new long[n];
            for(int i=0;i<n;i++)a[i]=Long.parseLong(next());
            return a;
        }
        char[] ncarr(){
            return next().trim().toCharArray();
            
            
        }
        
  
        int ni() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nl() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nd() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nstr() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }
    
    static void SegmentTree(int arr[], int n)
    {
        // Allocate memory for segment tree
        //Height of segment tree
        int x = (int) (Math.ceil(Math.log(n) / Math.log(2)));
 
        //Maximum size of segment tree
        int max_size = 2 * (int) Math.pow(2, x) - 1;
 
         int[] st = new int[max_size]; // Memory allocation
 
        constructSTUtil(arr, 0, n - 1, 0);
    }
    static int constructSTUtil(int arr[], int ss, int se, int si)
    {
        // If there is one element in array, store it in current node of
        // segment tree and return
        if (ss == se) {
            st[si] = arr[ss];
            return arr[ss];
        }
 
        // If there are more than one elements, then recur for left and
        // right subtrees and store the sum of values in this node
        int mid = getMid(ss, se);
        st[si] = Math.min(constructSTUtil(arr, ss, mid, si * 2 + 1) ,
                 constructSTUtil(arr, mid + 1, se, si * 2 + 2));
        return st[si];
    }
    static int getMid(int s, int e) {
        return s + (e - s) / 2;
    }
    static int getSum(int n, int qs, int qe)
    {
        // Check for erroneous input values
        if (qs < 0 || qe > n - 1 || qs > qe) {
           // System.out.println("Invalid Input");
            return -1;
        }
        return getSumUtil(0, n - 1, qs, qe, 0);
    }
    static int getSumUtil(int ss, int se, int qs, int qe, int si)
    {
        // If segment of this node is a part of given range, then return
        // the sum of the segment
        if (qs <= ss && qe >= se)
            return st[si];
 
        // If segment of this node is outside the given range
        if (se < qs || ss > qe)
            return Integer.MAX_VALUE;
 
        // If a part of this segment overlaps with the given range
        int mid = getMid(ss, se);
        return Math.min(getSumUtil(ss, mid, qs, qe, 2 * si + 1) ,
                getSumUtil(mid + 1, se, qs, qe, 2 * si + 2));
    }
    static void updateValue(int arr[], int n, int i, int new_val)
    {
        // Check for erroneous input index
        if (i < 0 || i > n - 1) {
//            System.out.println("Invalid Input");
            return;
        }
 
        // Get the difference between new value and old value
        int diff = new_val - arr[i];
 
        // Update the value in array
        arr[i] = new_val;
 
        // Update the values of nodes in segment tree
        updateValueUtil(0, n - 1, i, diff, 0);
    }
    static void updateValueUtil(int ss, int se, int i, int diff, int si)
    {
        // Base Case: If the input index lies outside the range of
        // this segment
        if (i < ss || i > se)
            return;
 
        // If the input index is in range of this node, then update the
        // value of the node and its children
        st[si] = st[si] + diff;
        if (se != ss) {
            int mid = getMid(ss, se);
            updateValueUtil(ss, mid, i, diff, 2 * si + 1);
            updateValueUtil(mid + 1, se, i, diff, 2 * si + 2);
        }
    }
    static boolean checkbound(int x , int y , int m , int n){
        if(x<0 || x>=m || y<0 || y>=n)return false;
        return true;
    }
    static void printmatrix(int[][] a){
        int m = a.length , n = a[0].length;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                System.out.print(a[i][j]+" ");
            }
            System.out.println();
        }
    }
    static void revarr(int[] a ){
        int i=0,j=a.length-1;
        while(i<j){
            int tem = a[i];
            a[i]=a[j];
            a[j]=tem;
            i++;j--;
        }
        //return a;
    }
    
    
    static int[] st;
    static FastReader br=new FastReader();//(new InputStreamReader(System.in));
/*

*/
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		int t=1;
		br=new FastReader();
	 //	t=br.ni();//Integer.parseInt(br.readLine().trim());
		StringBuilder sb=new StringBuilder();
		
	in1 :	while(t-->0)
		{
		    sb.append(solve()+"\n");
		}
			//			System.out.println("OUTPUT:::");
	
		System.out.println(sb);
	}
	static int solve(){
	    int n = br.ni();
	    int[][] a = br.tdiarr(n,2);
	    Arrays.sort(a , (x , y) -> x[0]-y[0]);
	    int p=n;
	    for(int i=0;i<n;i++){
	        if(a[i][0] > 0){
	            p=i;
	            break;
	        }
	    }
	    int ans1 = 0;
	    int i=p,j=p-1;
	    
	    while(true){
	        if(i>=n)break;
	        ans1 += a[i][1];
	        i++;
	        if(j<0)break;
	        ans1 += a[j][1];
	        j--;
	    }
	    int ans2 = 0;i=p;j=p-1;
	    while(true){
	        if(j<0)break;
	        ans2 += a[j][1];
	        j--;
	        if(i>=n)break;
	        ans2 += a[i][1];
	        i++;
	    }
	    return Math.max(ans1,ans2);
	    
	}
	



	
	
}