|시간 제한||메모리 제한||제출||정답||맞은 사람||정답 비율|
|1 초||128 MB||1||1||1||100.000%|
Because of the latest mishaps of their agents, Central Intelligence Agency of Byteland resolved to improve their activity. So far the biggest trouble has been a preparation of safe meetings of agents. Your program has to help in solving this. For a given description of the net of roads in Byteland and the initial positions of two agents, it should answer if their safe meeting is possible.
To consider a meeting safe the agents must hold to the following precautions:
Write a program which:
In the first line of the standard input, there are two integers a1 and a2 separated by a single space, where 1 ≤ n ≤ 250, 0 ≤ m ≤ n*(n-1).
In the second line there are two integers and separated by a single space, 1 ≤ a1, a2 ≤ n and a1≠a2, denoting respectively the starting positions of agents No 1 and No 2.
In the m following lines there are pairs of natural numbers a and b separated by single spaces, 1 ≤ a,b ≤ n and a≠b, denoting that there is a road from city a to city b.
There should be exactly one line in the standard input and it should contain:
6 7 1 5 1 2 4 5 2 3 3 4 4 1 5 4 5 6