class NOTOK:
    def __init__(this):
        this.__notok = {}
    def set(this,A,B):
        if (B in this.__notok) != True:
            this.__notok[A] = B
    def mov(this,A,B):
        this.__notok[A] = this.__notok.pop(B)
    def go(this,A,B):
        this.__notok[A](this.__notok[B])
    def get(this,A):
        return this.__notok.pop(A)
print('!'in'Hello world!')