#include<fstream>
using namespace std;
int main()
{
   char N,i,uc,s,n,j;
   ifstream f("cifra.in");
   ofstream g("cifra.out");
   f>>N;
   s=0;
   for(i=1;i<=N;i++)
   {
       if(i%10==0)s=s+0;
       if(i%10==5)s=s+5;
       if(i%10==1)s=s+1;
       if(i%10==6)s=s+6;
       else
       { uc=0;
         n=i;
         for(j=1;j<=n;j++)
       {
           uc=uc%10+n%10;
           n=n*n;
       }
       s=s+uc%10;

       }


   }
   g<<s%10;

}