var i,j,n,p,s,ct:longint;
    f1,f2:text;
    t:integer;
begin
assign(f1,'cifra.in');
reset(f1);
assign(f2,'cifra.out');
rewrite(f2);


        read(f1,n);

             s:=0;p:=1;
        for i:=1 to n do
        begin

                ct:=i;

                while ct>0 do
                begin

                p:=p*i;
                dec(ct);

                end;
        s:=s+p;
        end;

        write(f2,s mod 10);

close(f1);
close(f2);

end.