#include<bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    freopen("cifra.in", "r", stdin);
    freopen("cifra.out", "w", stdout);
    long long n;
    cin >> n;
    long long sum = 0;
    for (int i = 1; i <= n; i++){
        int termen = pow(i, i);
        termen %= 10;
        sum+=termen;
        sum %= 10;
    }
    cout << sum;
}