Sometimes Mister B has free evenings when he doesn't know what to do. Fortunately, Mister B found a new game, where the player can play against aliens.

All characters in this game are lowercase English letters. There are two players: Mister B and his competitor.

Initially the players have a string s consisting of the first a English letters in alphabetical order (for example, if a = 5, then s equals to "abcde").

The players take turns appending letters to string s. Mister B moves first.

Mister B must append exactly b letters on each his move. He can arbitrary choose these letters. His opponent adds exactly a letters on each move.

Mister B quickly understood that his opponent was just a computer that used a simple algorithm. The computer on each turn considers the suffix of string s of length a and generates a string t of length a such that all letters in the string t are distinct and don't appear in the considered suffix. From multiple variants of t lexicographically minimal is chosen (if a = 4 and the suffix is "bfdd", the computer chooses string t equal to "aceg"). After that the chosen string t is appended to the end of s.

Mister B soon found the game boring and came up with the following question: what can be the minimum possible number of different letters in string s on the segment between positions l and r, inclusive. Letters of string s are numerated starting from 1.

Input

First and only line contains four space-separated integers: a, b, l and r (1 ≤ a, b ≤ 12, 1 ≤ l ≤ r ≤ 109) — the numbers of letters each player appends and the bounds of the segment.

Output

Print one integer — the minimum possible number of different letters in the segment from position l to position r, inclusive, in string s.

Examples

Input

1 1 1 8


Output

2

Input

4 2 2 6


Output

3

Input

3 7 4 6


Output

1

Note

In the first sample test one of optimal strategies generate string s = "abababab...", that's why answer is 2.

In the second sample test string s = "abcdbcaefg..." can be obtained, chosen segment will look like "bcdbc", that's why answer is 3.

In the third sample test string s = "abczzzacad..." can be obtained, chosen, segment will look like "zzz", that's why answer is 1.
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 105;
int s[MAXN];
bool flag[MAXN];
int ans;
int a, b, l, r, m;
void DFS(int k, int p0) {
  if (k == 4) {
    int res = 0;
    memset(flag, 0, sizeof(flag));
    for (int i = l; i < r; ++i)
      if (!flag[s[i]]) flag[s[i]] = true, res++;
    ans = min(ans, res);
  } else {
    int id = 0;
    memset(flag, 0, sizeof(flag));
    if (k > 0)
      for (int i = p0 - a; i < p0; ++i)
        if (!flag[s[i]]) flag[s[i]] = true;
    for (int i = p0; i < p0 + a; ++i) {
      while (flag[id]) id++;
      flag[id] = true;
      s[i] = id;
    }
    for (int j = 0; j < 26; ++j) {
      for (int i = p0 + a; i < p0 + a + b; ++i) s[i] = j;
      DFS(k + 1, p0 + a + b);
    }
  }
  return;
}
int main() {
  ans = INT_MAX;
  cin >> a >> b >> l >> r;
  l--;
  m = 2 * (a + b);
  if (r - l >= m) {
    if (a <= b)
      ans = a + 1;
    else
      ans = 2 * a - b;
  } else {
    l %= m;
    r %= m;
    if (l > r) r += m;
    DFS(0, 0);
  }
  cout << ans << endl;
  return 0;
}
