题目描述
Problem Description
On a two-dimensional coordinate plane, you are given $2N+1$ points with distinct coordinates.
Takahashi wants to form many friendly pairs from these points.
Points can form a friendly pair if they satisfy one of the following conditions:
- The two points have the same $x$ coordinate or the same $y$ coordinate.
However, no point can be part of more than one friendly pair.
Takahashi wanted to make all points part of a friendly pair, but he realized it's impossible because the number of points is odd.
Therefore, he thought that if he removes just one point, he could then form $N$ friendly pairs from the remaining $2N$ points.
Determine for each point whether removing it allows forming $N$ friendly pairs from the remaining $2N$ points.
Input Format
The input is given from the standard input in the following format:
$N$ $X_1$ $Y_1$ $X_2$ $Y_2$ : $X_{2N+1}$ $Y_{2N+1}$
- The first line contains an integer $N(1 ≦ N ≦ 100,000)$, representing the number of points.
- The following $2N+1$ lines contain the position information of the points. The $i$-th line contains integers $X_i(1 ≦ X_i ≦ 2N+1)$ and $Y_i(1 ≦ Y_i ≦ 2N+1)$ separated by a space, indicating that the coordinates of the $i$-th point are $(X_i, Y_i)$.
- For $i ≠ j$, it holds that $X_i ≠ X_j$ or $Y_i ≠ Y_j$.
Output Format
Output to the standard output, with a newline at the end.
The output consists of $2N+1$ lines.
The $i$-th line should contain OK if removing the $i$-th point allows forming $N$ friendly pairs from the remaining $2N$ points, or NG if it does not.
Sample Input and Output
Sample Input #1
1
1 1
1 2
2 1
Sample Output #1
NG
OK
OK
Sample Input #2
2
1 1
1 2
2 2
2 3
3 3
Sample Output #2
OK
NG
OK
NG
OK
Sample Input #3
2
1 1
1 2
3 3
4 4
4 5
Sample Output #3
NG
NG
OK
NG
NG
Notes/Hints
Partial Points
If you solve the dataset that additionally satisfies the following constraints, you will be awarded 30 points:
- For all $i(1 ≦ i ≦ 2N)$, it holds that $X_i = X_{i+1}$ or $Y_i = Y_{i+1}$.
Sample Explanation 2
This input/output example satisfies the partial points constraints.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分