def find_depth(tree, target, depth=0):
    for key, subtree in tree.items():
        if key == target:
            return depth
        d = find_depth(subtree, target, depth + 1)
        if d is not None:
            return d
    return None

mall = {
    "전체": {
        "의류": {
            "상의": {},
            "하의": {
                "청바지": {},
                "치마": {}
            }
        },
        "전자기기": {
            "노트북": {},
            "스마트폰": {}
        }
    }
}

target = "청바지"
depth = find_depth(mall, target)
print(depth)