#include <stdio.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <map>
#include <iomanip>
#include <math.h> 
#include <stack>
#include <queue>
#include <bitset>
#include <cstdlib>
#include <tuple>
#include <cctype>
#include <ctype.h>
#include <set>
#include <sstream>

using namespace std;


int main() {
	long i, j, k;
	long n, m, p, q;

	cin >> n >> m >> p >> q;

	long mo = 1, cnt = 0;


	while (true)
	{
		if ( mo   >= p && mo  <= (p + q - 1) ) {
			n -= (m * 2);
			mo++;
			cnt++;
		}
		else {
			n -= m;
			mo++;
			cnt++;
		}

		if (mo >= 13) {
			mo -= 12;
		}

		if (n <= 0) {
			break;
		}
		
		
	}

	cout << cnt << endl;












	getchar();
	getchar();
	return 0;
}