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


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