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

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

    long long n,i,ii,s,t;
    fin>>n;
    s=0;
    for (i=1;i<=n;i++)
    {
       t=1;
       for (ii=1;ii<=i;ii++)
       {
          t=t*i;
       }

        s=s+t;
    }
    s=s%10;
    fout<<s;

    return 0;
}