Magic Square

Difficulty: 1200 2000 ms 128 MB

implementation

Is the N×N matrix a magic square — all rows, all columns and both diagonals sharing the same sum? (Values need not be distinct.)

Input: the first line has N and N; the next N lines each have N integers.

Output: YES or NO.

Constraints:

• 1 ≤ N ≤ 100

Sample Tests

3 3
2 7 6
9 5 1
4 3 8

YES

2 2
1 2
3 4

NO

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