#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
template<class T = int> using V = vector<T>;
template<class T = int> using VV = V< V<T> >;
template<class T> void assign(V<T>& v, int n, const T& a = T()) { v.assign(n, a); }
template<class T, class... U> void assign(V<T>& v, int n, const U&... u) { v.resize(n); for (auto&& i : v) assign(i, u...); }

int main() {
  cin.tie(NULL); ios::sync_with_stdio(false);
  int n, m, p, q; cin >> n >> m >> p >> q;
  int res = 1;
  while (true) {
    int t = (res - 1)% 12 + 1;
    if (p <= t and t < p + q) n -= 2 * m;
    else n -= m;
    if (n <= 0) return cout << res << '\n', 0;
    res++;
  }
}