private static int checkMatrix(int[][] matrix) {
    int maxNegativeColumn = -1;
    for (int j = matrix[0].length-1; j >= 0; j--) {
        for (int i = 0; i < matrix.length;i++){
            if (matrix[i][j] >= 0){
                break;
            }
            if(i == matrix.length-1)
                maxNegativeColumn = j;
        }
        if(maxNegativeColumn != -1)
            break;
    }
    return maxNegativeColumn;
}