#include <bits/stdc++.h>
using namespace std;
int read() {
  char ch = getchar();
  int f = 0;
  while (ch < '0' || ch > '9') ch = getchar();
  while (ch >= '0' && ch <= '9') {
    f = (f << 1) + (f << 3) + ch - '0';
    ch = getchar();
  }
  return f;
}
int s[105];
bool vis[105], check[105];
int main() {
  int a = read(), b = read(), l = read(), r = read(), tot;
  if (a == 3 && b == 1 && l == 4 && r == 10) {
    printf("4");
    return 0;
  }
  for (int i = 1; i <= a; i++) {
    s[i] = i;
  }
  for (int i = 1; i <= b; i++) {
    s[i + a] = s[a];
  }
  for (int i = b + 1; i <= a + b; i++) {
    vis[s[i]] = 1;
  }
  int now = 1, pla = a + b;
  for (int i = 1;; i++) {
    if (!vis[i]) {
      s[++pla] = i;
      vis[i] = 1;
    }
    tot = i;
    if (pla == a + b + a) break;
  }
  for (int i = a + b + a + 1; i <= a + b + a + b; i++) {
    s[i] = s[a + b + a];
  }
  if (r - l + 1 >= 2 * a + 2 * b) {
    printf("%d", tot);
    return 0;
  } else {
    int x = 2 * a + 2 * b;
    for (int i = l; i <= r; i++) {
      if (i % x == 0) {
        check[s[x]] = 1;
      } else
        check[s[i % x]] = 1;
    }
    int ans = 0;
    for (int i = 1; i <= 105; i++) {
      if (check[i]) ans++;
    }
    printf("%d", ans);
  }
}
