#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    
    bool flag=false;
    
    int ans=0;
    while(s>0){
        s-=p;
        if(!flag)
        p-=d;
        
        if(p<=m){
            p=m;
            flag=true;
        }
        ans++;
        if(s<0)
            ans--;
        
        //ans++;
        
        
        
    }
    return ans;
    
   /* 
    if((p-m )%d==0)
        n=(p-m)/d;
    else{
        n=(p-m)/d;
        n=n+1;
        
    }
    
    int sum= (n*(2*p+(n-1)*(-d)))/2;
    if(sum>=s){
        s-=sum;
        int newn=s/m;
        return newn+n;
    }
    else{
        int count=0;
        while(s>0){
            s-=p;
            count++;
            
            
            
        }
        
        
    }
    
    */
    
    
    // Return the number of games you can buy
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}