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


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