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