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 main() {
  int A, B, L, R;
  cin >> A >> B >> L >> R;
  if ((R - L) >= 2 * (A + B)) {
    if (A > B)
      cout << 2 * A - B << endl;
    else
      cout << A + 1 << endl;
    return 0;
  }
  int l = (L - 1) % (A + B) + 1;
  int r = l + R - L;
  vector<int> str;
  for (int i = 0; i < A; ++i) {
    str.push_back(i);
  }
  for (int j = 0; j < B; ++j) {
    str.push_back(str[A - 1]);
  }
  int k;
  if (A > B) {
    k = B;
  } else {
    k = A - 1;
  }
  for (int i = 0; i < k; ++i) {
    str.push_back(i);
  }
  for (int i = A; i < A + A - k; ++i) str.push_back(i);
  for (int j = 0; j < B; ++j) {
    str.push_back(str[A + B + A - 1]);
  }
  for (int i = 0; i < A; ++i) {
    str.push_back(i);
  }
  for (int j = 0; j < B; ++j) {
    str.push_back(str[A - 1]);
  }
  if (l == A + B && (r == 3 * (A + B) - 2)) {
    if (str[r - 1] < A && str[r - 1] >= k) str[l - 1] = str[r - 1];
  }
  set<int> dif;
  for (int i = l - 1; i < r; ++i) {
    dif.insert(str[i]);
  }
  cout << dif.size();
  return 0;
}
