#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i<(n); ++i)
using namespace std;
using ll=long long;
int main(){
    int n,m,p,q;
    cin>>n>>m>>p>>q;
    int cnt=0;
    int ans=0;
    while(n>0){
        ans++;
        cnt++;
        if(cnt==13){
            cnt=1;
        }
        if(p<=cnt&&cnt<=p+q-1){
            n-=m;
        }
        n-=m;
    }
    cout<<ans<<endl;
}