#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define repi(i, a, b) for (int i = (a); i < (b); i++)
#define all(a) (a).begin(), (a).end()

using namespace std;
using i32 = int;
using i64 = long long;
using f64 = double;
using vi32 = vector<i32>;
using vvi32 = vector<vi32>;
using vi64 = vector<i64>;
using vvi64 = vector<vi64>;

template<typename T> inline bool amin(T &x, T y) { if (y < x) { x = y; return true; } return false; }
template<typename T> inline bool amax(T &x, T y) { if (x < y) { x = y; return true; } return false; }

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m, p, q;
  cin >> n >> m >> p >> q;
  int ans = 1;
  int month = 1;
  while (true) {
    if (month >= p && month < p + q) {
      n -= m * 2;
    } else {
      n -= m;
    }
    if (n <= 0) break;
    ans++;
    month += 1;
    if (month == 13) month = 1;
  }
  cout << ans << endl;
  return 0;
}