#include <iostream>
using namespace std;
int main(int argc, char* argv[])
{
	int N,M,P,Q;
	cin>>N>>M>>P>>Q;
	int Sum=0;
	int mon=0;
	int i;
	while (Sum<N){
		for (i=1;i<P;i++){
			Sum+=M;
			mon++;
			if (Sum>=N){
				cout<<mon<<endl;
				return 0;
			}
		}
		for (i=1;i<=Q;i++){
			Sum+=2*M;
			mon++;
			if (Sum>=N){
				cout<<mon<<endl;
				return 0;
			}
		}
		while (mon<12){
			Sum+=M;
			mon++;
			if (Sum>=N){
				cout<<mon<<endl;
				return 0;
			}
		}			
	}
	cout<<mon<<endl;
	return 0;
}