Given a matrix that contains only 1s and 0s, find the largest X shape which contains only 1s, with the same arm lengths and the four arms joining at the central point.

Return the arm length of the largest X shape.

Assumptions

• The given matrix is not null, has size of N * M, N > = 0 and M > = 0.

Examples

{ {0, 0, 0, 0},

{1, 1,1, 1},

{0,1, 1, 1},

{1, 0,1, 1} }

the largest X of 1s has arm length 2.

Approach: Similar to the largest cross. the direction get changed. we need preprocess the left__up--> right__bottom

right_ up-->left\ bottom , left_bottom-->right_up, and right_bottom to left_up directions. _

Step2: for each position m[i][j], find the min(4 preprocessed matrix in that position). if (m[i][j] > max) max = m[i][j] return max.