#include<iostream>
#include<string>
using namespace std;
#define int long long
#define rep(i,n) for(int i = 0; i < n; i++)
#define INF (long long)(1e18)
#define MOD (int)(1e9+7)
#define MAX_V

signed main(){
	int N, M, P, Q, temp, count = 0;
	
	cin>>N>>M>>P>>Q;
	
	temp = N/(Q*M*2+(12-Q)*M);
	N -= temp*(Q*M*2+(12-Q)*M);
	// cout<<temp<<endl;
	count += temp*12;
	while(N > 0){
		// if(N >= (Q*M*2+(12-Q)*M)){
			// count += 12;
			// N -= Q*M*2+(12-Q)*M;
			// continue;
		// }
		for(int i = 1; i <= 12; i++){
			if(P <= i && i < P+Q){
				N -= M*2;
			}else N-= M;
			
			// count++;
			if(N < 0)break;
			count++;
		}
	}
	cout<<count<<endl;
	
	
	return 0;
}