#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
using namespace std;
#define lint long long int
/*
vector<char>al(26);
al = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
vector<char>AL(26);
AL = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
*/

int main() {
	int N, M, P, Q;
	cin >> N >> M >> P >> Q;
	int i = 1;
	int I;
	while (N > 0) {
		I = i % 12;
		if (I == 0) {
			I += 12;
		}
		if (P <= I && I <= P+Q-1) {
			N -= M * 2;
		}
		else {
			N -= M;
		}
		i++;
	}
	cout << i - 1 << endl;
}