#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int p , d,  m , s;
    cin>>p >> d>> m>>s;
    int c = 0;
    while(s > 0){
        if(s >= p){
            s -= p;
            c ++;
            p = max(p - d , m);
        }else{
            break;
        }
    }
    cout<<c;
    return 0;
}