#include<bits/stdc++.h>
using namespace std;
struct arr
{
  int a1;
  int a2;
  int a3;
};
int main()
{
    int p,d,m,s,c,flag=0,sum=0,ans=0;
    cin>>p>>d>>m>>s;
    c=p;
    while(c>m)
    {
        if(sum+c<s)
        sum+=c;
        else
        {flag=1;break;}
        c-=d;
        ans++;
    }
    if(!flag)
    {while(sum+m<=s)
    {
        sum+=m;
        ans++;
    }}
    cout<<ans<<endl;
}