def unique_paths(rows, cols):
    if rows == 0 or cols == 0:
        return 0
    dp = [[0] * cols for _ in range(rows)]
    dp[0][0] = 1
    for r in range(rows):
        for c in range(cols):
            if r == c == 0:
                continue
            dp[r][c] = (dp[r - 1][c] if r else 0) + (dp[r][c - 1] if c else 0)
    return dp[-1][-1]