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