Good Order
A network at the oce consists of several nodes and bidirectional cables, connecting them with the nextproperties.
Each cable is connecting exactly two nodes.
Cable cannot connect the node with itself.
Any two nodes are connected directly with no more than one cable.
The information between any two nodes can be passed through one or more cables and intermediate nodes (i.e. any two nodes are linked by this network).
CEO wants the network to be in the good order, namely, he wants to have exactly one node with exactly one cable connected to it, exactly two nodes with exactly two cables connected to it and so on till n, i.e. for any 1 ≤ i ≤ n the network must contain exactly i nodes with exactly i cables connected to it. Sergeant does not allow any other nodes and cables except for that.
Your task is to build good order network for given integer n or consider that it is impossible to do it.
Input
Contains one integer n (1 ≤ n ≤ 239) - the parameter of the network.
Output
If it is impossible to build good order network for given n, print -1. Otherwise, list all the cables in the network. Each cable must be listed at the new line, description of one cable must contain two 1-based indices of the nodes connected by the cable.