#include <fstream>
#include <iostream>
using namespace std;
ifstream f ("cifra.in");
ofstream g ("cifra.out");
int main ()
{
	int t,i,j,n,p=1,s=0,c;
	f>>t;
	if (t<1) return 0;
	if (t>30000) return 0;
	for (j=1;j<=t;j++)
	{
		f>>n;
		if (n<1) return 0;
		if (n>=10000) return 0;
		for (i=1;i<=n;i++)
		{
			p=i*i;
			s=s+p;
		}
		c=s%10;
	}
	g<<c;
	return 0;
}