Problem Statement

There is a square grid of dimensions $10^9 \\times 10^9$. The cells are numbered $(1, 1)$ through $(10^9, 10^9)$. Cell $(i, j)$ is in the $i$-th row from the top, and the $j$-th column from the left. Initially, $N$ cells $(x_1, y_1), \\ldots, (x_N, y_N)$ are black, and all other cells are white.

Snuke can perform the following operation an arbitrary number of times:

• Choose an integer $x (1 \\leq x \\leq 10^9 - 1)$ and an integer $y (1 \\leq y \\leq 10^9 - 2)$, and flip (black to white, white to black) the colors of the following six cells: $(x, y), (x, y+1), (x, y+2), (x+1, y), (x+1, y+1), (x+1, y+2)$

Compute the minimum possible number of black cells after the operations.

Constraints

• $1 \\leq N \\leq 10^5$
• $1 \\leq x_i, y_i \\leq 10^9$
• $(x_i, y_i)$ are pairwise distinct.
• All values in the input are integers.

Input

Input is given from Standard Input in the following format:

$N$ $x_1 \\ y_1$ $:$ $x_N \\ y_N$

Output

Print the answer.

Sample Input 1

9
1 2
1 3
2 1
2 3
2 4
3 2
3 3
3 4
4 2

Sample Output 1

3

In the diagram below, the $j$-th letter of the $i$-th string from the top represents the cell $(i, j)$. # is black, . is white.

.##.
#.##
.###
.#..

->

#...
.#.#
.###
.#..

->

#...
..#.
....
.#..