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;
long long a, b, l, r, size_ = 1, cr[26];
char str[1000];
int main() {
  cin >> a >> b >> l >> r;
  long long ss = (r - l + 1), tot = 0;
  l -= (l / (a + b) - (l % (a + b) == 0)) * (a + b);
  if (a <= b) {
    bool ok = 0;
    while (size_ <= 500) {
      for (int i = 0; i < a; i++) str[size_++] = 'a' + i;
      if (ok) str[size_ - 1] = 'a' + a;
      for (int i = 0; i < b; i++) {
        str[size_++] = 'a' + a - 1;
      }
      ok = 1;
    }
  } else {
    while (size_ <= 500) {
      long long x = a, ptr = 0;
      while (x) {
        while (cr[ptr]) ptr++;
        str[size_++] = 'a' + ptr;
        ptr++;
        x--;
      }
      char ch = str[size_ - (a - b)];
      for (int i = 0; i < b; i++) str[size_++] = ch;
      memset(cr, 0, sizeof(cr));
      for (int i = size_ - a; i < size_; i++) {
        cr[str[i] - 'a'] = 1;
      }
    }
  }
  memset(cr, 0, sizeof(cr));
  for (int i = l; i < min(l + ss, 400ll); i++)
    if (cr[str[i] - 'a'] == 0) cr[str[i] - 'a'] = 1, tot++;
  long long min_ = tot;
  if (a > b) {
    memset(cr, 0, sizeof(cr));
    size_ = 1;
    while (size_ <= 500) {
      long long x = a, ptr = 0;
      while (x) {
        while (cr[ptr]) ptr++;
        str[size_++] = 'a' + ptr;
        ptr++;
        x--;
      }
      char ch = str[size_ - 1];
      for (int i = 0; i < b; i++) str[size_++] = ch;
      memset(cr, 0, sizeof(cr));
      for (int i = size_ - a; i < size_; i++) {
        cr[str[i] - 'a'] = 1;
      }
    }
  }
  memset(cr, 0, sizeof(cr)), tot = 0;
  for (int i = l; i < min(l + ss, 400ll); i++)
    if (cr[str[i] - 'a'] == 0) cr[str[i] - 'a'] = 1, tot++;
  min_ = min(min_, tot);
  cout << min_ << "\n";
}
