#include <bits/stdc++.h>

using namespace std;

int main()
{
    int p,d,m,s,sum=0,count=0;
    cin>>p>>d>>m>>s;
    
    while(1)
    {
        sum=sum+p;
        if(sum<=s)
            count++;
        
        p=p-d;
        if(p<m)
            p=m;
        
        if(sum>s)
            break;
    }
    cout<<count;
}