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#3560

Making Colored Paper 2 (Quadtree) 4s 512MB

Problems

Jaewoo is studying divide and conquer.

So he solved problem 1335: Making Colored Paper.

Wanting to study more, Jaewoo thought of the following problem.

 

Given a square with a side length that is a power of 2, if all numbers in the square are 0, it is represented as 0; if all numbers are 1, it is represented as 1.

Otherwise, if the square contains both 0 and 1, the area is represented by an uppercase X, and the area is divided into four equal parts, recursively applying the same rule.

The order of calling the four divided areas is top-left, top-right, bottom-left, and bottom-right.

 

For example, if the following information is given:

8

1 0 1 1 1 1 1 1
0 1 1 1 1 1 1 1
0 0 0 0 1 1 1 1
0 0 0 0 1 1 1 1
1 1 0 0 0 0 0 0
1 1 0 0 0 0 0 0
0 0 1 1 0 0 0 0
0 0 1 1 0 0 0 0​

 

Following the rules above, the following result is produced.

XXX10011001X10010​  


Input

The length of one side, N, is entered in the first row. 

(8 <= N <= 1024, N is a power of 2) Information is entered in the next single row.​


Output

Outputs a string created according to the rules.


Example

8

1 0 1 1 1 1 1 1
0 1 1 1 1 1 1 1
0 0 0 0 1 1 1 1
0 0 0 0 1 1 1 1
1 1 0 0 0 0 0 0
1 1 0 0 0 0 0 0
0 0 1 1 0 0 0 0
0 0 1 1 0 0 0 0
XXX10011001X10010​


Source

KOI 전국 2001 중1 응용

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