def traverse_map(*, tree_map, down, right, row=0, col=0, count=0):
    """Traverse tree_map starting in top-right and return how many trees we hit"""
    if row >= len(tree_map):
        return count
    line = tree_map[row]
    if line[col % len(line)] == "#":
        count += 1
    return traverse_map(
        tree_map=tree_map,
        down=down,
        right=right,
        col=col + right,
        row=row + down,
        count=count,
    )