#include<fstream.h>
int main()
{
ifstream f("cifra.in");
ofstream g("cifra.out");
 long n,k,v[100],s,i,j;
 f>>n;
  s=0;
 for(i=1;i<=n;i++)
 { f>>v[i];
  k=1;
  for(j=1;j<=v[i];j++)
 {k=k*v[i];
  k=k%10;   
 }
 s=s+k;
 }
 s=s%10;
 g<<s;
 f.close();
 g.close();
 return 0;
}