#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
int main(void) {
  int N, M, P, Q;
  cin >> N >> M >> P >> Q;
  vector<int> NumDrop(13);
  for(int i = 1; i <= 12; i++) {
    if(P <= i && i < P + Q) {
      NumDrop[i] = 2 * M;
    } else {
      NumDrop[i] = M;
    }
  }
  int ans = 0;
  while(N > 0) {
    for(int i = 1; i <= 12 && N > 0;
        N -= NumDrop[i], i++, ans++) {
    }
  }
  cout << ans << endl;
  return 0;
}