#include<fstream>
#include<cmath>
using namespace std;
int main()
{
    int a[30],n,i,s;
    s=0;
    ifstream f("cifra.in", ios::in);
    ofstream g("cifra.out", ios::out);
    f>>n;
    for(i=1;i<=n;i++)
    f>>a[i];
    for(i=1;i<=n;i++)
    s=s+(a[i]^a[i]);
    g<<s%10;
    return 0;}