#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,count=0;
    unsigned long long int sum=0;
   int a= scanf("%d %d %d %d",&p,&d,&m,&s);
    if(p<=s&&p>=m){
       // count=1;
        while(sum<=s){
            count++;
            sum+=p;
            if(p-d>=m) p=p-d;
            else p=m;
            //p=p-d;
            
            //if(p<m) break;
            
        }
     if(sum>s) count--;
        
    }
    
    
    printf("%d\n",count);
    return 0;
}