import collections

def solve(N, M, data):

    count = collections.Counter()
    unionset = []
    for d in data:
        count.update(d)
        d0s = None
        d1s = None
        for s in unionset:
            if d[0] in s:
                d0s = s
            elif d[1] in s:
                d1s = s
        if d0s == None and d1s == None:
            unionset.append(set([d[0], d[1]]))
        elif d0s != None and d1s == None:
            d0s.add(d[1])
        elif d0s == None and d1s != None:
            d1s.add(d[0])
        else:
            unionset.remove(d0s)
            unionset.remove(d1s)
            n = d0s.union(d1s)
            unionset.append(n)

    oddcount = 0
    for val in count.values():
        if val % 2 == 1:
            oddcount += 1

    return "YES" if oddcount <= 2 and len(unionset) == 1 else "NO"


if __name__ == '__main__':
    N, M = map(int, input().split())
    d = []
    for _ in range(0, M):
        d.append(list(map(int, input().split())))
    print(solve(N, M, d))