import re


def is_circle_number(footnotes_marker):
    """Check whether footnotes marker is number in circle or not and if so
       returns equivalent number.

    Args:
        footnotes_marker (str): footnotes marker
    Returns:
        str: number inside the circle
    """
    value = ""
    number = re.search("[①-⓪]", footnotes_marker)
    if number:
        circle_num = {
            "⓪": "0",
            "①": "1",
            "②": "2",
            "③": "3",
            "④": "4",
            "⑤": "5",
            "⑥": "6",
            "⑦": "7",
            "⑧": "8",
            "⑨": "9",
            "⑩": "10",
            "⑪": "11",
            "⑫": "12",
            "⑬": "13",
            "⑭": "14",
            "⑮": "15",
            "⑯": "16",
            "⑰": "17",
            "⑱": "18",
            "⑲": "19",
            "⑳": "20",
        }
        value = circle_num.get(number[0])
    return value