var f1,f2:text;
    i,j,x,n:longint;
begin
        assign(f1,'tije.in');
        reset(f1);
        assign(f2,'tije.out');
        rewrite(f2);
        read(f1,n);
        for i:=n downto 2 do
                writeln(f2,i,' ',n+1);
        for x:=1 to n do
        begin
                for i:=n downto x+1 do
                        writeln(f2,x,' ',i);
                for i:=1 to n-1 do
                        writeln(f2,n+1,' ',x);
                for i:=n downto x+1 do
                begin
                        for j:=1 to x do
                                writeln(f2,i,' ',i+1);
                        if i<>x+1 then
                                writeln(f2,i,' ',n+1);
                end;
        end;
        close(f1);
        close(f2);
end.