#include <bits/stdc++.h>
using namespace std;
int a, b;
long long l, r;
int op;
int dfs(int ch, vector<int> v) {
  if (v.size() >= 2 * (a + b)) {
    int cnt = 0;
    int vis[30] = {0};
    if (op == 1) {
      for (int i = 2 * (a + b) - a; i < 2 * (a + b); i++) {
        if (v[i] < a) return 0x3f3f3f3f;
      }
      for (int i = l; i < 2 * (a + b); i++) {
        if (vis[v[i]] == 0) cnt++;
        vis[v[i]] = 1;
      }
      for (int i = 0; i <= r; i++) {
        if (vis[v[i]] == 0) cnt++;
        vis[v[i]] = 1;
      }
    } else {
      for (int i = l; i <= r; i++) {
        if (vis[v[i]] == 0) cnt++;
        vis[v[i]] = 1;
      }
    }
    return cnt;
  }
  for (int i = 0; i < b; i++) v.push_back(ch);
  int vis[30] = {0};
  for (int i = v.size() - 1; i >= v.size() - a; i--) vis[v[i]] = 1;
  vector<int> box;
  for (int i = 0; i < 26; i++)
    if (vis[i] == 0) box.push_back(i);
  if (box.size() < a) return 0x3f3f3f3f;
  for (int i = 0; i < a; i++) {
    v.push_back(box[i]);
  }
  int ans = 0x3f3f3f3f;
  for (int i = 0; i < 26; i++) {
    ans = min(ans, dfs(i, v));
  }
  return ans;
}
int main() {
  scanf("%d%d%lld%lld", &a, &b, &l, &r);
  long long T = 2 * (a + b);
  int ans = 0x3f3f3f3f;
  if (r - l + 1 < T) {
    l--;
    r--;
    l %= T;
    r %= T;
    if (l > r) op = 1;
    vector<int> v;
    for (int i = 0; i < a; i++) v.push_back(i);
    for (int i = 0; i < 26; i++) {
      ans = min(ans, dfs(i, v));
    }
  } else {
    if (b >= a)
      ans = a + 1;
    else
      ans = 2 * a - b;
  }
  printf("%d\n", ans);
  return 0;
}
