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


int main() {
    int s,p,d,m,i,sum=0,n=0;
    cin>>p>>d>>m>>s;
while(sum<=s)
{
    sum=sum+p;
  
    n++;
    if(p>m+d)
    p=p-d;
    else 
        p=m;
}
    
    cout<<n-1;
    
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}