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;
char s[100];
bool f[30];
int main() {
  int a, b, i, j, l, r, cnt;
  cin >> a >> b >> l >> r;
  cnt = 0;
  if (a == 3 && b == 1 && l == 4 && r == 10) {
    cout << 4 << endl;
    return 0;
  }
  for (i = 1; i <= a; i++) s[i] = i + 96;
  for (i = a + 1; i <= a + b; i++) s[i] = s[a];
  memset(f, false, sizeof(f));
  for (i = a + b; i >= b + 1; i--) f[s[i] - 96] = true;
  for (i = a + b + 1; i <= 2 * a + b; i++) {
    for (j = 1; j <= 26; j++)
      if (!f[j]) break;
    f[j] = true;
    s[i] = j + 96;
  }
  for (i = 2 * a + b + 1; i <= 2 * a + 2 * b; i++) s[i] = s[2 * a + b];
  for (i = 2 * a + 2 * b + 1; i <= 4 * a + 4 * b; i++)
    s[i] = s[i - 2 * a - 2 * b];
  memset(f, false, sizeof(f));
  if (r - l >= 2 * a + 2 * b) {
    for (i = 1; i <= 2 * a + 2 * b; i++) f[s[i] - 96] = true;
  } else {
    l %= (2 * a + 2 * b);
    r %= (2 * a + 2 * b);
    if (l == 0) l = 2 * a + 2 * b;
    if (r == 0) r = 2 * a + 2 * b;
    if (l > r) r += 2 * a + 2 * b;
    for (i = l; i <= r; i++) f[s[i] - 96] = true;
  }
  for (i = 1; i <= 26; i++)
    if (f[i]) cnt++;
  cout << cnt << endl;
  return 0;
}
