#include <iostream>
#include <fstream>
using namespace std;
int n,s,i,j,S;
int main()
{
    ifstream f("cifra.in");
    ofstream g("cifra.out");
    f>>n;
    for(i=1;i<=n;i++)
    {
        s=i;
        for(j=1;j<=i-1;j++)
        {
            s=(s*i)%10;
        }
        S=(S+s)%10;
    }
    g<<S;


    return 0;
}