import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
     *
     * 最大正方形
     * @param matrix char字符型二维数组 
     * @return int整型
     */
    public int solve (char[][] matrix) {
        // write code here
        
        int m = matrix.length;
        if (m == 0) {
            return 0;
        }
        int n = matrix[0].length;
        int[][] dp = new int[m+1][n+1];
        int size = 0;
        for (int i = 1;i <= m ; i++) {
            for (int j = 1;j <= n; j++){
                if (matrix[i-1][j-1] == '1') {
                    dp[i][j] = Math.min(dp[i-1][j],Math.min(dp[i][j-1],dp[i-1][j-1])) + 1;
                    size = Math.max(dp[i][j],size); 
                }
            }
        
        }
        return size*size;
    }
}