#include <bits/stdc++.h>
using namespace std;


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