#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define set(x,y) memset(x,y,sizeof(x))
#define pii pair<ll,ll>
ll p,d,m,s;
ll t,n,a[1000006];
int main() {
    cin>>p>>d>>m>>s;
    ll count=0;
    while(p<=s && p>=m){
        count++;
        s-=p;
        p-=d;
    }
    if(p>s){
        cout<<count;
    }
    else{
        ll t = s/m;
        count+= t;
        cout<<count;
    }
    return 0;
}