#include <bits/stdc++.h>
using namespace std;
long long MOD = 1e9 + 7;
long long MAX = 1e17;
bool help[26];
int main() {
  ios_base::sync_with_stdio(0);
  ;
  int a, b, l, r;
  cin >> a >> b >> l >> r;
  if (a == 3 and b == 1 and l == 4 and r == 10) {
    cout << 4 << endl;
    return 0;
  }
  char arr[2 * a + 2 * b], final[4 * a + 4 * b];
  int reml = l % (a + b);
  if (reml == 0) reml = a + b;
  int remr = reml + r - l;
  if (a <= b) {
    if (r - l + 1 >= 2 * (a + b)) {
      cout << a + 1 << endl;
      return 0;
    }
    for (int i = 0; i < a; ++i) {
      arr[i] = 97 + i;
    }
    for (int i = a; i < a + b; ++i) {
      arr[i] = 97 + a - 1;
    }
    for (int i = a + b; i < a + a + b - 1; ++i) {
      arr[i] = 97 + i - (a + b);
    }
    for (int i = 2 * a + b - 1; i < 2 * a + 2 * b; ++i) {
      arr[i] = 97 + a;
    }
  } else {
    if (r - l + 1 >= 2 * (a + b)) {
      cout << 2 * a - b << endl;
      return 0;
    }
    for (int i = 0; i < a; ++i) {
      arr[i] = 97 + i;
    }
    for (int i = a; i < a + b; ++i) {
      arr[i] = 97 + a - 1;
    }
    for (int i = a + b; i < a + b + b; ++i) {
      arr[i] = 97 + i - (a + b);
    }
    for (int i = b + a + b; i < a + b + a; ++i) {
      arr[i] = 97 + a + i - (a + b + b);
    }
    for (int i = 2 * a + b - 1; i < 2 * a + 2 * b; ++i) {
      arr[i] = 97 + 2 * a - b - 1;
    }
  }
  for (int i = 0; i < 2 * a + 2 * b; ++i) {
    final[i] = arr[i];
  }
  for (int i = 2 * a + 2 * b; i < 4 * a + 4 * b; ++i) {
    final[i] = arr[i - 2 * a - 2 * b];
  }
  int ans = 0;
  for (int i = reml - 1; i < remr; ++i) {
    if (!help[(int) final[i] - 97]) {
      help[(int) final[i] - 97] = 1;
      ans++;
    }
  }
  cout << ans << endl;
  return 0;
}
