#include <iostream>
#include <fstream>

using namespace std;

int main()
{


    ifstream f("cifra.in");
    ofstream g("cifra.out");
    int n,i,nr,p,j,s;

    f>>n;
    for(i=1;i<=n;i++){
                     f>>nr;
                     p=1;
                     for(j=1;j<=nr;j++){
                                      p=(p*nr)%10;
                                       s=(s+p)%10;
                                       }

                                       }

    g<<s;
    f.close();
    g.close();
    return 0;
}