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;
void add(string &s, int a) {
  int used[26] = {}, n = s.length();
  for (int i = 0; i < a; ++i) {
    used[s[n - 1 - i] - 'a'] = 1;
  }
  for (int i = 0; i < 26; ++i) {
    if (!used[i]) {
      s += ('a' + i);
      a--;
    }
    if (a == 0) break;
  }
}
int main() {
  long long a, b, l, r;
  cin >> a >> b >> l >> r;
  l--;
  r--;
  if (r - l + 1 > 2 * (a + b)) {
    if (a <= b)
      cout << a + 1 << endl;
    else
      cout << 2 * a - b << endl;
    return 0;
  }
  if (l / (a + b) > 1) {
    int x = l / (a + b) - 2;
    l -= x * (a + b);
    r -= x * (a + b);
  }
  int ans = 10000;
  for (char c1 = 'a'; c1 <= 'z'; c1++) {
    for (char c2 = 'a'; c2 <= 'z'; c2++) {
      for (char c3 = 'a'; c3 <= 'z'; c3++) {
        for (char c4 = 'a'; c4 <= 'z'; c4++) {
          string s;
          for (int i = 0; i < a; ++i) s += ('a' + i);
          for (int i = 0; i < b; ++i) s += c1;
          add(s, a);
          for (int i = 0; i < b; ++i) s += c2;
          add(s, a);
          for (int i = 0; i < b; ++i) s += c3;
          add(s, a);
          for (int i = 0; i < b; ++i) s += c4;
          add(s, a);
          set<char> st;
          for (int i = l; i <= r; ++i) st.insert(s[i]);
          ans = min(ans, (int)st.size());
        }
      }
    }
  }
  cout << ans << endl;
  return 0;
}
