Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ACM-ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

A. Bear and Friendship Condition

time limit per test

1 secondmemory limit per test

256 megabytesinput

standard inputoutput

standard outputBear Limak examines a social network. Its main functionality is that two members can become friends (then they can talk with each other and share funny pictures).

There are *n* members, numbered 1 through *n*. *m* pairs of members are friends. Of course, a member can't be a friend with themselves.

Let A-B denote that members A and B are friends. Limak thinks that a network is reasonable if and only if the following condition is satisfied: For every three distinct members (X, Y, Z), if X-Y and Y-Z then also X-Z.

For example: if Alan and Bob are friends, and Bob and Ciri are friends, then Alan and Ciri should be friends as well.

Can you help Limak and check if the network is reasonable? Print "YES" or "NO" accordingly, without the quotes.

Input

The first line of the input contain two integers *n* and *m* (3 ≤ *n* ≤ 150 000, ) — the number of members and the number of pairs of members that are friends.

The *i*-th of the next *m* lines contains two distinct integers *a*_{i} and *b*_{i} (1 ≤ *a*_{i}, *b*_{i} ≤ *n*, *a*_{i} ≠ *b*_{i}). Members *a*_{i} and *b*_{i} are friends with each other. No pair of members will appear more than once in the input.

Output

If the given network is reasonable, print "YES" in a single line (without the quotes). Otherwise, print "NO" in a single line (without the quotes).

Examples

Input

4 3

1 3

3 4

1 4

Output

YES

Input

4 4

3 1

2 3

3 4

1 2

Output

NO

Input

10 4

4 3

5 10

8 9

1 2

Output

YES

Input

3 2

1 2

2 3

Output

NO

Note

The drawings below show the situation in the first sample (on the left) and in the second sample (on the right). Each edge represents two members that are friends. The answer is "NO" in the second sample because members (2, 3) are friends and members (3, 4) are friends, while members (2, 4) are not.

Codeforces (c) Copyright 2010-2017 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Nov/19/2017 06:08:12 (c2).

Desktop version, switch to mobile version.

User lists

Name |
---|