Given an m x n matrix mat where every row is sorted in strictly increasing order, return the smallest common element in all rows.

If there is no common element, return -1.

Example 1:

Input: mat = [[1,2,3,4,5],[2,4,5,8,10],[3,5,7,9,11],[1,3,5,7,9]]
Output: 5

Example 2:

Input: mat = [[1,2,3],[2,3,4],[2,3,5]]
Output: 2

class Solution {
    public int smallestCommonElement(int[][] A) {
        int[] count = new int[10001];
        int n = A.length, m = A[0].length;
        for (int j = 0; j < m; ++j)
            for (int i = 0; i < n; ++i)
                if (++count[A[i][j]] == n)
                    return A[i][j];
        return -1;
    }
}