#include <bits/stdc++.h>
using namespace std;

typedef unsigned long long ll;
typedef std::pair<int, int> P;

#define For(i, a, b) for(int i = (a); i < (b); i++)
#define Rep(i, n) For(i, 0, (n))
#define Rrep(i, n) for(int i = (n - 1); i >= 0; i--)
#define All(i, x) for(typeof(x.begin()) i = x.begin(); i != x.end(); i++)
#define ReAll(i, x) for(typeof(x.end()) i = x.end(); i != x.begin(); i--)
#define pb push_back

const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const int MAX = 100000;
const int INF = 1e9;
const int MOD = 1000000007;
const string END = "\n";

void solve(){
	int n, m, p, q; cin >> n >> m >> p >> q;
	int a[12] = {};
	For(i, 1, 13){
		if(i >= p && i <= p + q - 1){
			a[i-1] = m * 2;
		}else{
			a[i-1] = m;
		}
	}
	bool flag = false;
	int ans = 0;
	while(n > 0){
		Rep(i, 12){
			if(flag) break;
			n -= a[i];
			ans += 1;
			if(n <= 0) flag = true;
		}
	}
	cout << ans << END;
}

int main(){
	cin.tie(0);
   	ios::sync_with_stdio(false);
	solve();
	return 0;
}