문제
상근이는 프로그램을 디버깅할 때, 버그와 프로그램 메모리에서 정사각형 킬러가 깊은 관계가 있다는 것을 알게 되었다.
프로그램 메모리는 1과 0으로만 이루어진 R행 C열 행렬로 이루어져 있다.
정사각형 킬러란 프로그램 메모리에서 한 글자보다 많은 문자로 이루어진 정사각형 부분 행렬 중에서, 180도 돌렸을 때와 원래 부분 행렬이 같은 것이다.
예를 들어, 프로그램 메모리가 아래 그림과 같을 때, 정사각형 킬러는 3가지가 있다.
상근이는 가장 큰 정사각형 킬러의 크기와 버그 사이의 관계가 궁금해졌다. 프로그램 메모리가 주어졌을 때, 가장 큰 정사각형 킬러의 크기를 구하는 프로그램을 작성하시오. 정사각형 킬러의 크기는 부분 행렬의 행의 개수 또는 열의 개수와 같다. 위의 그림에서 정사각형 킬러의 크기는 순서대로 2, 2, 3이다.
출력
첫째 줄에 가장 큰 정사각형 킬러의 크기를 출력한다. 만약 정사각형 킬러가 없다면 -1을 출력한다.
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