#include <fstream>
using namespace std;
ifstream fin("cifra.in");
ofstream fou("cifra.out");
int n, s, i ,j, s2;
int main (){
    fin >> n;
    fin.close()';
    i = 1;
    while (i <= n){
        j = 1;
        s2 = 1;
        while (j <= i){
            s2 = s2 * i;
            j = j + 1;}
        s = s + s2;
        i = i + 1;}
        fou << s % 10;
        fou.close();
















    return 0;}