#include <iostream.h>
#include <fstream.h>
fstream f("cifra.in",ios::in);
fstream g("cifra.out",ios::out);
int main()
{
float t,n; int x,s,c,i,p;
s=0;
p=1;
for (i=1;i<=n;i++) {
		     x=i;
		     for (x=i;x>0;x--)
				  {
                                  p=p*i;
				  x=x-1;
				  }
		     s=s+p;
		     p=1;
                   }
c=s%10;
g<<c;
f.close();
g.close();
return 0;
}