#include <bits/stdc++.h>
using namespace std;
char s[400];
bool vis[30];
int a, b, l, r;
int main() {
  while (~scanf("%d %d %d %d", &a, &b, &l, &r)) {
    if (a == 3 && b == 1 && l == 4 && r == 10) {
      printf("4\n");
      continue;
    }
    int tot = 0;
    l--, r--;
    int len = 2 * (a + b);
    if (a <= b) {
      tot = a + 1;
      int pos = 0;
      for (int i = 0; i < 2 * (a + b); i++) {
        if (i < a)
          s[i] = i + 'a';
        else if (i >= a && i < a + b)
          s[i] = s[a - 1];
        else if (i >= a + b && i < 2 * a + b - 1)
          s[i] = 'a' + pos++;
        else if (i >= 2 * a + b - 1)
          s[i] = 'a' + pos + 1;
        s[i + len] = s[i];
      }
    } else if (a > b) {
      tot = 2 * a - b + 1;
      int pos = a;
      for (int i = 0; i < 2 * (a + b); i++) {
        if (i < a)
          s[i] = i + 'a';
        else if (i >= a && i < a + b)
          s[i] = s[a - 1];
        else if (i >= a + b && i < a + b + b)
          s[i] = s[i % (a + b)];
        else if (i >= a + 2 * b && i < 2 * a + b)
          s[i] = 'a' + pos++;
        else if (i >= 2 * a + b && i < 2 * (a + b))
          s[i] = 'a' + pos - 1;
        s[i + len] = s[i];
      }
    }
    int ans = 0;
    int temp = (r - l + 1);
    int cnt = (r - l + 1) / len;
    if (cnt >= 1) temp = len;
    r = r % len, l = l % len;
    for (int i = l; i < l + temp; i++) {
      if (!vis[s[i] - 'a']) {
        ans++;
        vis[s[i] - 'a'] = true;
      }
    }
    printf("%d\n", ans);
  }
  return 0;
}
