def gridChallenge(grid):
    columns = [0] * len(grid[0])
    for index in range(len(grid)):
        row = [ord(c) for c in grid[index]]
        row.sort()        
        for c in range(len(row)):
            if columns[c] > row[c]:
                return 'NO'
            columns[c] = row[c]
    return 'YES'``