#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int main() {
  int n, m, p, q; cin >> n >> m >> p >> q;
  int cnt = 0, month = 1;
  while (n > 0) {
    if (p <= month && month < p + q) n -= 2 * m;
    else n -= m;
    cnt++;
    month++;
    if (month == 13) month = 1;
  }
  cout << cnt << endl;
  return 0;
}