program dame;
var n:longint;
        f,g:text;




procedure iofile;
begin
        assign(f,'dame.in');
        reset(f);
        assign(g,'dame.out');
        rewrite(g);
        readln(f,n);
        close(f);
end;



procedure asezare(n:longint);
var x,y:longint;
begin
        x:=1;
        y:=1;
        while (x<=n)and(y<=n) do
                begin
                        writeln(g,x,' ',y);
                        x:=x+2;
                        y:=y+1;
                end;
        dec(x,2);
        dec(y);
        x:=x-1;
        y:=y+2;
        while x>=2 do
                begin
                        writeln(g,x,' ',y);
                        x:=x-2;
                        y:=y-1;
                end;
end;




begin
        iofile;
        if n mod 2=1 then
                begin
                        writeln(g,n);
                        asezare(n);
                        close(g);
                        end else
                                begin
                        writeln(g,n);
                asezare(n-1);
                writeln(g,n,' ',n);
                close(g);
                end;
end.