#include <bits/stdc++.h>
using namespace std;
template <typename T>
void out(T x) {
  cout << x << endl;
  exit(0);
}
using ll = long long;
const ll mod = 1e9 + 7;
const int maxn = 1e6 + 5;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int a, b, l, r;
  cin >> a >> b >> l >> r;
  l--;
  r--;
  auto gen = [&](int x, int y) {
    string s;
    for (int i = 0; i < a; i++) {
      s += char('a' + i);
    }
    for (int iter = 0; iter < 16; iter++) {
      if (iter % 2 == 1) {
        string suffix = s.substr(int(s.length()) - a);
        set<char> used;
        for (char c : suffix) used.insert(c);
        char mex = 'a';
        for (int i = 0; i < a; i++) {
          while (used.count(mex)) mex++;
          s += mex;
          used.insert(mex);
        }
      } else {
        for (int i = 0; i < b; i++) {
          if (iter % 4 == 0) {
            s += char('a' + x);
          } else {
            s += char('a' + y);
          }
        }
      }
    }
    return s;
  };
  auto solve = [&](string s, int l, int r) {
    set<char> seen;
    int len = (int)s.size() - a;
    for (int i = 0; i < a; i++) {
      if (l <= i && i <= r) {
        seen.insert(s[i]);
      }
    }
    s = s.substr(a);
    l = max(l, a);
    if (r - l + 1 > 4 * (int)s.size()) {
      for (char c : s) seen.insert(c);
    } else {
      for (int i = l; i <= r; i++) {
        seen.insert(s[(i - a) % len]);
      }
    }
    return (int)seen.size();
  };
  int ans = 1e9;
  for (int i = 0; i < 26; i++) {
    for (int j = 0; j < 26; j++) {
      string s = gen(i, j);
      int cur = solve(s, l, r);
      ans = min(ans, cur);
    }
  }
  cout << ans << endl;
  return 0;
}
