Check if a Graph Is a Linked List
Given an undirected graph with
v vertices and e edges, you are asked to determine if the graph is actually a linked list.
Input
The first line of the input contains two integers
v (1 ≤ v ≤ 100 000) and e (1 ≤ e ≤ 100 000).The following
e lines contain pairs of integers v1, v2 (1 ≤ v1, v2 ≤ v) which means that the vertex v1 is connected to the vertex v2 and vice versa.Output
The program should print
Yes if the graph is a linked list and No otherwise.Examples
Input | Output |
6 5
3 2
2 1
5 6
4 6
1 4 | Yes |
6 4
3 2
2 1
5 6
4 6 | No |
Constraints
Time limit: 2 seconds
Memory limit: 512 MB
Output limit: 1 MB