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 l, r, a, b, dif, t, x, lit, poz;
bool uz[27];
char s[1001];
int main() {
  cin >> a >> b >> l >> r;
  dif = min(500, r - l);
  l = l % (a + b);
  if (l == 0) l = a + b;
  r = l + dif;
  if (l <= a) {
    for (int i = l; i <= min(a, r); i++) s[++poz] = i;
    l = a + 1;
    t = 1;
  } else {
    for (int i = l; i <= min(a + b, r); i++) s[++poz] = 1;
    l = a + b + 1;
    memset(uz, 0, sizeof(uz));
    for (int i = poz; i >= max(1, poz - a + 1); i--) uz[s[i]] = 1;
    lit = 1;
    t = 2;
  }
  x = 0;
  while (l <= r) {
    if (t == 1) {
      x++;
      s[++poz] = s[poz - 1];
      l++;
      if (x == b) {
        memset(uz, 0, sizeof(uz));
        for (int i = poz; i >= max(1, poz - a + 1); i--) uz[s[i]] = 1;
        lit = 1;
        t = 2;
        x = 0;
      }
    } else {
      x++;
      while (uz[lit] == 1) lit++;
      s[++poz] = lit;
      l++;
      uz[lit] = 1;
      if (x == a) {
        t = 1;
        x = 0;
      }
    }
  }
  memset(uz, 0, sizeof(uz));
  for (int i = 1; i <= poz; i++) {
    uz[s[i]] = 1;
  }
  int nr = 0;
  for (int i = 1; i <= 26; i++) nr += uz[i];
  cout << nr;
  return 0;
}
