#include <iostream>
using namespace std;
int main()
{
int a, b,c,d,n;

cout<<"a1";
cin >> a;
cout<<"a2";
cin >> b;
cout<<"a3";
cin >> c;
cout<<"N";
cin  >>n ;
while(n > 0) {
d = (a + b + c) % 10;
a = b;
b = c;
c = d;
n--;
}
cout << d <<endl;
return 0;
}