PT07Y - Is it a tree

You are given an unweighted, undirected graph. Write a program to check if it's a tree topology.

Input

The first line of the input file contains two integers N and M --- number of nodes and number of edges in the graph (0 < N <= 10000, 0 <= M <= 20000). Next M lines contain M edges of that graph --- Each line contains a pair (u, v) means there is an edge between node u and node v (1 <= u, v <= N).

Output

Print YES if the given graph is a tree, otherwise print NO.

Example

Input:
3 2
1 2
2 3

Output:
YES

Added by:Thanh-Vy Hua
Date:2007-03-28
Time limit:0.5s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO
Resource:Co-author Amber

hide comments
2011-04-22 04:44:35 kiransk
is the input graph connected?
2011-04-19 07:03:38 albertg
YES. THAT'S RIGHT.
2011-01-17 21:45:39 :D
One test case per file.
2009-08-21 08:15:54 Marko Ivankovic
Read about it here: http://en.wikipedia.org/wiki/Tree_(graph_theory)

Last edit: 2009-08-21 08:16:22
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