var s,n,i,j,z:longint;
    f,g:text;
begin
assign(f,'cifra.in');
assign(g,'cifra.out');
reset(f); rewrite(g);
readln(f,n);
s:=0;
for i:=1 to n do begin
                z:=1;
                for j:=1 to i do z:=z*i;
                s:=s+z;
                end;
write(g,s mod 10);
close(f);
close(g);
end.























end.