#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;

int main()
{
    freopen("cifra.in", "r", stdin);
    freopen("cifra.out", "w", stdout);
    int s, i, p, n, j;
    cin>>n;
    s=0;
    for (i=1; i<=n; i++)
    {
        p=1;
        for (j=1; j<=i; j++)
        {
            p=p*i;
            p=p%10;
        }
        s=s+p; s=s%10;
    }
    cout<<s;
    return 0;
}