#include<fstream>
using namespace std;
long long n,s=0,i,j=0,aux=0;
ifstream fin("cifra.in") ;
ofstream fout("cifra.out") ;
void citire()
{
	fin>>n;
}
void putere()
{
	for(i=1;i<=n;++i)
    for(aux=1;aux<=n;++aux)
	{
		j=i*i;
		s=s+j;
    }
    s=s/n;
}
void afisare()
{
	fout<<s%10;
}
int main()
{
    citire();
    putere();
    afisare();
	fin.close () ;
    fout.close();
    return 0;
}