#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 */   
  long long  int p,m,d,s;
    cin>>p>>m>>d>>s;
   long long int sum=0;int c=0;
for(int i=0;sum<=s;i++)
{sum=sum+p;
 p=p-m;
 if(p<d)
     p=d;
 
 
 if(sum<=s)c++;
     
    
}
    cout<<c;
    return 0;
}