//100 de pucte pe campion problema ucif
#include<fstream.h>

ifstream fin("cifra.in");
ofstream fout("cifra.out");

int putere(long x)
{int c=1,p;
for(p=1;p<=x;p++)
  {c=c*x;
  if(c>=10) c=c%10;
  }
return c%10;
}

int main()
{long n,i;
int ucif=0;
fin>>n;
for(i=1;i<=n;i++)
    {ucif=ucif+putere(i);
     if(ucif>=10) ucif=ucif%10;
    }
fout<<ucif;
fin.close();
fout.close();
return 0;
}