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

int main() {
    long long p,d,m,s,count = 0;
    cin>>p>>d>>m>>s;
    while(s >= p)
    {
        s -= p;
        if(p-d >= m)
        p -= d; 
        else p = m;
        count++;
    }   
    cout<<count<<endl;
    return 0;
}