#include<iostream>
using namespace std;
int main()
{
int a,b,c,d,e,sum=0;
cin>>a>>b>>c>>d;
e=a+b;
sum=e;
for(int i=1;i<=d;i++)
{
e=a+b;
a=b;
b=e;
if(e>c)
break;
sum=sum+e;
}
cout<<sum;
return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
int a,s;
cin>>a;
for(int i=1;i<=a;i++)
{
for(int j=1;j<=a;j++)
{
if(j==1||j==a)
cout<<"|";
else if(i==a/2+1)
cout<<"-";
else
cout<<"a";
}
cout<<endl;
}
return 0;
}