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


int main() {
    int p,d,m,s,coun_t=0;
    scanf("%d%d%d%d",&p,&d,&m,&s);
    while(s>=p)
    {
        coun_t++;
        s=s-p;
        p=p-d;
        if(m>p)
            p=m;
    }
    printf("%d",coun_t);/* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}