#include<bits/stdc++.h>
#define md 1000000007
using namespace std;



int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
int p,d,m,s;
cin>>p>>d>>m>>s;
int count=0,sum=0;
while(1){
    if(p<=m)
        sum+=m;
    else
        {sum+=p;
            p-=d;}
    if(sum>s)
        break;
    else
        count++;
}
cout<<count;
return 0;
}