#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
using namespace std;
typedef long long ll;
const int mod=1e9+7;
int main(){
	int n,m,p,q;
	cin>>n>>m>>p>>q;
	p--;
	for(int i=0;;i++){
		n-=m;
		if(p<=i%12&&i%12<p+q)
			n-=m;
		if(n<=0)
			cout<<i+1<<endl,exit(0);
	}
}