from typing import Literal


def gridChallenge(grid: list[str]) -> Literal["NO", "YES"]:
    _grid = iter(grid)
    last_row = sorted(next(_grid))
    for row in _grid:
        row = sorted(row)
        if any(i < j for i, j in zip(row, last_row)):
            return "NO"
        last_row = row
    return "YES"