Cards — Eolymp

Input

The first line contains a single integer $N$ ( $2 \leq N \leq 100000$ 2 \leq N \leq 100\,000, $N$ is an even integer) — the number of cards. Each of the following $N$ lines contains two integers $a_{i}$ a_i and $b_{i}$ b_i ( $- 2000 \leq a_{i}, b_{i} \leq 2000$ -2000 \leq a_i, b_i \leq 2000; $i = 1 \dots N$ i = 1\ldots N). These are the numbers written on both sides of the $i$ -th card.

Output

The only line should contain the minimal value that can be obtained by placing all the cards into the expression as described above.

Examples

Example 1

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Note

1: Cards are put into the expression in this order: $1$ , $2$ , $3$ , $5$ , $4$ , $6$ .

$(- 8) - 5 + (- 3) - 7 + (- 7) - 4 = - 34$ (-8) - 5 + (-3) - 7 + (-7) - 4 = -34

2: Cards are put into the expression in this order: $2$ , $1$ , $4$ , $3$ , $5$ , $8$ , $6$ , $9$ , $7$ , $10$ .

$62 - 70 + 59 - 81 + 40 - 76 + 35 - 85 + 57 - 96 = - 155$ 62 - 70 + 59 - 81 + 40 - 76 + 35 - 85 + 57 - 96 = -155