from collections import deque
from collections import defaultdict

n, m = (int(x) for x in input().split())
l = defaultdict(list)
for i in range(m):
    a, b = (int(x) for x in input().split())
    a -= 1
    b -= 1
    l[str(a)+"up"].append(str(b)+"down")
    l[str(a)+"down"].append(str(b)+"up")
    l[str(b)+"up"].append(str(a)+"down")
    l[str(b)+"down"].append(str(a)+"up")

def bfs(u):
    queue = deque([u])
    S = set(); S.add(u)
    while queue:
        v = queue.popleft()
        for i in l[v]:
            if not i in S:
                queue.append(i)
                S.add(i)
    return S


for i in range(n):
    d = bfs(str(i) + "up")
    if str(i) + "down" not in d:
        print("No")
        exit()

print("Yes")