n, m = map(int, input().split())
edges = [[] for _ in range(n)]
for _ in range(m):
    u, v = map(int, input().split())
    u -= 1
    v -= 1
    edges[u].append(v)
    edges[v].append(u)

stack = [u]
used = [False] * n
used[u] = True
while stack:
    pos = stack.pop()
    for npos in edges[pos]:
        if used[npos]:
            continue
        used[npos] = True
        stack.append(npos)
odd = 0
for i in range(n):
    if not used[i] and edges[i]:
        print("NO")
        exit()
    if len(edges[i]) & 1:
        odd += 1
if odd <= 2:
    print("YES")
else:
    print("NO")