#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n, m, p, q;
  cin >> n >> m >> p >> q;
  int ans = 0;
  while (n > 0) {
    ans++;
    int mo = (ans - 1) % 12 + 1;
    n -= m;
    if (p <= mo && mo < p + q) n -= m;
  }
  cout << ans << endl;
  return 0;
}