题目描述

Mr Aoligei became the boss of the network company. There are $n$ houses (including the company) in his network, N-1 bidirectional channels to connect the nodes, and there always exists a route from any house to another house. Each channel is 1 kilometer long. The company is house $h$ and the money a house needs to pay is the distance of the route between the company and the house.

Now, Mr Poo lives in house $t$. He wants to know how much money does he need to pay.

输入格式

The first line of the input file contains two integers: $n, t, h$.

Following N-1 lines represent the channels in the original network of SN, each pair $(a, b)$ denote that there is a channel between node a and node b.

输出格式

Print out the money he needs to pay.

输入输出样例

Input #1:

5 4 3
3 1
3 4
3 2
4 5

Output #1:

1