#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <fstream>
#include <set>
#include <utility>
#include <algorithm>
#include <queue>
#include <stack>
#include <deque>
#include <numeric>
#include <sstream>
#include <list>
#include <map>
#include <stdlib.h>
#include <time.h>

#define rep(i,p,n) for(int i=(int)p;i<(int)n;i++)
#define repp(i,p,n) for(int i=(int)p;i>=(int)n;i--)
#define Sort(x) sort(x.begin(),x.end());
#define ll long long
#define INF 2000000000

using namespace std;
int main() {
	int n, m, p, q;
	int month = 0,ans=0;
	cin >> n >> m >> p >> q;
	p--; q--;
	vector<int> v(12,1);
	rep(i, p, p + q+1) {
		v[i] = 2;
	}

	while (n > 0) {
		n-=m*v[month];
		month++; ans++;
		if (month > 11)month = 0;
	}
	cout << ans << endl;


	return 0;
}