#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <array>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
#include <memory>
#include <regex>
using namespace std;

int main()
{
    int n, m, p, q;
    cin >> n >> m >> p >> q;
    -- p;

    int i = 0;
    while(n > 0){
        n -= m;
        if(p <= i % 12 && i % 12 < p + q)
            n -= m;
        ++ i;
    }
    cout << i << endl;

    return 0;
}