#include<bits/stdc++.h>
#include <string>
#define ll long long
 
using namespace std;
 
unsigned long mod = 1000000007; 


ll solve(ll p, ll d, ll m, ll s){
	if(p > s || m > s)return 0;
	if(p == s)return 1;
    //if(m > s)return 0;
	
	ll sum = p;
    ll curr = p;
    
	if((curr-d) < m)curr =m; 
    else curr-=d;
    
    ll count=1;
    
    if(curr < m)curr=m;
	
	while(sum+curr <= s){
		//if(curr < m)curr =m;
		sum+=curr;   
        
        if((curr-d) < m)curr =m; 
        else curr-=d;
        
        count++;
	}
    
	return count;
}
 
int main(){
    ll p,d,m,s;
    cin>>p>>d>>m>>s;
    
    cout << solve(p, d, m, s) <<"\n";
	
	
	return 0;
}