#include <bits/stdc++.h>
using namespace std;
int main(){
  long long n,m,p,q,ans=0,month=1;
  cin >> n >> m >> p >> q;
  q+=p-1;
  if(q>12){
    q%=12;
  }
  while(1){
    if(n<=0){
      cout << ans << endl;
      return 0;
    }
    if(p<=month and month<=q){
      n-=2*m;
    }else{
      n-=m;
    }
    ans++;
    month++;
    if(month==13) month=1;
  }
}