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

int main()
{
    int p,d,m,s;
    cin >> p >> d >> m >> s;

    int sum=0;
    int c = 0;
    while(true){
        s -=  p;
        p = max(p-d,m);
        if(s >= 0)
            ++c;
        else
            break;
    }
    cout << c;
    return 0;
}