#include <bits/stdc++.h>
using namespace std;
const static int inf = 1e9 + 7;
const static int N = 1e4 + 5;
char x[65];
int c[26];
vector<int> d;
int main() {
  int a, b, l, r;
  scanf("%d%d%d%d", &a, &b, &l, &r);
  for (int i = 0; i < 26; ++i) c[i] = 0;
  for (int i = 0; i < a; ++i) x[i] = 'a' + i;
  for (int i = a; i < a + b; ++i) x[i] = x[i - 1];
  for (int i = 0; i < 26; ++i) c[i] = 0;
  for (int i = a + b - 1; i >= b; --i) c[x[i] - 'a']++;
  int y = (l - 1) % (a + b);
  for (int i = a + b; i < a + b + a; ++i)
    for (int j = 0; j < 26; ++j)
      if (c[j] == 0) {
        x[i] = 'a' + j;
        c[j] = 1;
        break;
      }
  for (int i = a + b + a; i < a + b + a + b; ++i) x[i] = x[i - 1];
  for (int i = 0; i < 26; ++i) c[i] = 0;
  for (int i = a + b + a + b - 1; i >= a + b + b; --i) c[x[i] - 'a']++;
  d.clear();
  for (int i = y; i < a + b + a - 1; ++i) d.push_back(x[i] - 'a');
  int w = 0;
  for (int i = 0; i < d.size(); ++i)
    if (c[d[i]] == 0) {
      x[a + b + a + b + w] = 'a' + d[i];
      c[d[i]]++;
      w++;
    }
  for (int i = a + b + a + b + w; i < a + b + a + b + a; ++i)
    for (int j = 0; j < 26; ++j)
      if (c[j] == 0) {
        x[i] = 'a' + j;
        c[j] = 1;
        break;
      }
  int z = r - l;
  for (int i = 0; i < 26; ++i) c[i] = 0;
  for (int i = y; i < a + b + a + b + a && i <= z + y; ++i) c[x[i] - 'a']++;
  int sum = 0;
  for (int i = 0; i < 26; ++i)
    if (c[i] != 0) sum++;
  printf("%d\n", sum);
  return 0;
}
