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>
#pragma GCC optimize("-O3")
using namespace std;
void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  _main();
}
int A, B, L, R;
int naive(int off) {
  string s = "";
  for (int i = 0; i < A; i++) s += char('a' + i);
  while (s.length() <= R + 1) {
    char cc = s[s.length() - 1 - off];
    for (int i = 0; i < B; i++) s += cc;
    set<char> se;
    for (int j = 0; j < A; j++) se.insert(s[s.length() - 1 - j]);
    char c = 'a';
    for (int i = 0; i < A; i++) {
      while (se.count(c)) c++;
      s += c;
      c++;
    }
  }
  set<char> ss;
  for (int i = L; i < R + 1; i++) {
    ss.insert(s[i]);
  }
  return ss.size();
}
void _main() {
  cin >> A >> B >> L >> R;
  L--;
  R--;
  int d = L - L % (A + B);
  L -= d;
  R -= d;
  R = min(R, 1010);
  int ans = 101010101;
  for (int i = 0; i < A; i++) {
    ans = min(ans, naive(i));
  }
  cout << ans << endl;
}
