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;
int a, b, l, r, i, j, k, e, res, x, y, w, ans;
int s[1000], xx[100];
bool c[25];
void solve() {
  k = 0;
  for (e = 0; e <= 3; e++) {
    memset(c, true, sizeof(c));
    if (e > 0)
      for (i = 1; i <= a; i++) c[s[k + 1 - i]] = false;
    for (i = 1; i <= 24; i++)
      if (c[i]) {
        s[++k] = i;
        if (k == e * (a + b) + a) break;
      }
    for (i = 1; i <= b; i++) s[++k] = xx[e + 1];
  }
  memset(c, true, sizeof(c));
  ans = 0;
  for (i = x; i <= y; i++) {
    if (c[s[i]]) ans++;
    c[s[i]] = false;
  }
  res = min(res, ans);
}
void attempt(int tt) {
  if (tt == 5) {
    solve();
    return;
  }
  int i;
  for (i = 1; i <= 24; i++) {
    xx[tt] = i;
    attempt(tt + 1);
  }
}
int main() {
  scanf("%d %d %d %d", &a, &b, &l, &r);
  if (r - l >= (a + a + b + b)) {
    if (a > b) printf("%d", 2 * a - b);
    if (a <= b) printf("%d", a + 1);
    return 0;
  }
  x = l % (a + a + b + b);
  if (x == 0) x = a + a + b + b;
  y = x + (r - l);
  res = 2 * a;
  attempt(1);
  printf("%d", res);
}
