#include <iostream>
#include <fstream>
#include <math.h>
#include <string.h>

using namespace std;

int main()
{
        ifstream f("cifra.in");
        ofstream g("cifra.out");

    int t,i ;
    f >> t ;

    string	numar;
	char last;

     long long suma = 0 ;

      for (i=1;i<=t;i++)

      {   getline(f,numar);
          //f.getline(numar,102);
            last = numar[numar.length()-1];
          suma += last-48;
          suma = suma % 10 ;
      }

            g<<suma;

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