#include <iostream.h>
#include <fstream.h>
int i,x,s,us,up,n,j;
ifstream f("ucif.in");
ofstream g("ucif.out");
int main()
{
	f>>n;
	us=0;
	for (i=1;i<=n;i++)
	{
		up=1;
		for (j=1;j<=i;j++)
			up=up*i%10;
		us=(us+up)%10;
	}
	
	g<<us;
	return 0;
}