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

int main ()
{char a[1000];
 int u[13]={0,1,4,9,6,5,6,9,4,1};
 long t,i,s=0;
 int c;
 ifstream fin("cifra.in");
 fin>>t;
 for (i=1;i<=t;i++) 
 {fin>>a;
  c=a[strlen(a)-1]-48;
  s+=u[c];
 }
 ofstream fout("cifra.out");
 fout <<s%10;
 fout.close();
 fin.close();
}