#include <fstream>
using namespace std;
ifstream f("cifra.in");
ofstream g("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 k=0;
f>>n;
for(i=1;i<=n;i++)
    {
		k = k+putere(i);
     if(k >= 10) 
		 k = k % 10;
    }
g<<k;
return 0;
}