#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int n,m,p,q;
  cin>>n>>m>>p>>q;
  p--;
  Int ans=0;
  while(1){
    for(Int i=0;i<12;i++){
      if(p<=i&&i<p+q) n-=m*2;
      else n-=m;
      ans++;
      if(n<=0) break;
    }
    if(n<=0) break;
  }
  cout<<ans<<endl;
  return 0;
}