rattatosk.py

def main():
    from sys import stdin
    rl=stdin.readline
    rl()
    rl()
    root = rl().rstrip()
    ratatosk = rl().rstrip()
    parent = {}
    count = 0
    for node in stdin:
        node = node.split()
        t=node.pop(0)
        for n in node:
            parent[n]=t
        while parent.has_key(ratatosk):
            ratatosk=parent[ratatosk]
            count+=1
        if ratatosk == root:
            print count
            return
if __name__ == '__main__':
    main()