#include<iostream>
#include<vector>
#include<algorithm>
#include<functional>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<unordered_map>
#include<climits>
#include<cstdlib>
#include<cmath>
#include<string>
#include<iomanip>

using namespace std;

#define INF 1 << 29
#define LL long long int

LL const MOD = 1000000007;

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

    LL n,m,p,q;
    cin >> n >> m >> p >> q;

    LL ans = 0;
    LL month = 1;
    while(n > 0){
        ans++;
        if(month >= p && month < p+q){
            n -= 2*m;
        }else{
            n -= m;
        }
        month++;
        if(month > 12){
            month = 1;
        }
    }

    cout << ans << endl;
    
    return 0;
}