#include <bits/stdc++.h>

using namespace std;

int main() {
    int p,t=0,c=0;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    
    while(1)
    {
        t=t+p; 
        p=p-d;
        if(p<m)
            p=m;
        if(t<=s)
            c++;
        else
            break;
        
    }
    cout <<c<< endl;
    return 0;
}