#include <fstream>
#include <cmath>
using namespace std;

    ifstream fin("cifra.in");
    ofstream fout("cifra.out");

int main()
{
        int x,k = 1, n = 0;
        fin >> x;
        for ( int i = 1; i <= x; i ++){

        k += i * i;
        }
        n = k % 10;
        fout << n;

		return 0;

	}