import sys
from collections import deque

def main():
    N, M = map(int, sys.stdin.readline().split())
    adj = [[] for _ in range(N)]
    degree = [0] * N

    for _ in range(M):
        Sa, Sb = map(int, sys.stdin.readline().split())
        adj[Sa].append(Sb)
        adj[Sb].append(Sa)
        degree[Sa] += 1
        degree[Sb] += 1

    # Check connectivity using BFS
    visited = [False] * N
    start = None
    for i in range(N):
        if degree[i] > 0:
            start = i
            break
    if start is None:
        # All nodes are isolated, but M >=1 so this can't happen
        print("NO")
        return

    q = deque()
    q.append(start)
    visited[start] = True

    while q:
        u = q.popleft()
        for v in adj[u]:
            if not visited[v]:
                visited[v] = True
                q.append(v)

    # Check if all nodes with edges are visited
    connected = True
    for i in range(N):
        if degree[i] > 0 and not visited[i]:
            connected = False
            break

    if not connected:
        print("NO")
        return

    # Count odd degrees
    odd_count = 0
    for d in degree:
        if d % 2 != 0:
            odd_count += 1

    if odd_count == 0 or odd_count == 2:
        print("YES")
    else:
        print("NO")

if __name__ == "__main__":
    main()