#include <bits/stdc++.h>
using namespace std;

int main(){
  int n, m, p, q;
  cin >> n >> m >> p >> q;

  int cnt = 0;
  int year = 1;
  while(n > 0){
    if(p <= year && year < p+q){
      n -= 2 * m;
    }else{
      n -= m;
    }
    year = (year + 1);
    if(year > 12) year = 1;
    cnt++;
  }

  cout << cnt << endl;
  return 0;
}