#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repr(i, a, b) for(int i = a; i >= b; i--)
#define int long long
#define all(a) a.begin(), a.end()
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
using namespace std;
typedef pair<int, int> P;
const int mod = 1000000007;
const int INF = 1e15;

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m, p, q;
    cin >> n >> m >> p >> q;
    for(int i = 0;; i++){
        int tmp = i % 12;
        if(p - 1 <= tmp && tmp < p - 1 + q) n -= 2 * m;
        else n -= m;
        if(n <= 0){
            cout << i + 1 << endl;
            return 0;
        }
    }
}