3373번 - Cards 다국어

Adam has a fancy for numbers. Once he found a batch of empty paper cards in his drawer, wrote random numbers on both sides of each card and thought of the following puzzle: what smallest possible value can be obtained by putting all cards in an arbitrary order (and upturned if necessary) to the expression of the following form:

After a while Adam came up with a solution. Could you do that too? Write a program to solve the puzzle described above.

The first line contains the number of cards N (2 ≤ N ≤ 100 000, N is an even integer). Each of the following N lines contains two integers a_i and b_i (-2000 ≤ a_i, b_i ≤ 2000; i = 1…N). These are the numbers written on separate sides of the i-th card.

The first and the only line should contain the minimal value that can be obtained by putting all the cards to the expression as described above.