class UnionFind:
    def __init__(self, n):
        self.parent = [-1] * n
        self.n = n
        self.cnt = n

    def root(self, x):
        if self.parent[x] < 0:
            return x
        else:
            self.parent[x] = self.root(self.parent[x])
            return self.parent[x]

    def merge(self, x, y):
        x = self.root(x)
        y = self.root(y)
        if x == y:
            return False
        if self.parent[x] > self.parent[y]:
            x, y = y, x
        self.parent[x] += self.parent[y]
        self.parent[y] = x
        self.cnt -= 1
        return True

    def same(self, x, y):
        return self.root(x) == self.root(y)

    def size(self, x):
        return -self.parent[self.root(x)]

    def count(self):
        return self.cnt

    def groups(self):
        res = [[] for _ in range(self.n)]
        for i in range(self.n):
            res[self.root(i)].append(i)
        return [group for group in res if group]


def is_eulerian(digraph):
    n = len(digraph)
    diffs = [0] * n  # diff = outdeg - indeg
    uf = UnionFind(n)
    vs = set([])
    for v in range(n):
        for nxt_v in digraph[v]:
            diffs[v] += 1
            diffs[nxt_v] -= 1
            uf.merge(v, nxt_v)
            vs.add(v)
            vs.add(nxt_v)
    if len(vs) - n + uf.count() != 1:
        # 非連結な路が存在するので有向オイラー路が存在しない
        return False, -1, -1
    if diffs.count(0) == n:
        # 有向オイラー閉路
        return True, -1, -1
    s, t = [], []
    for v, diff in enumerate(diffs):
        if diff == 1:
            s.append(v)
        if diff == -1:
            t.append(v)
    if len(s) == 1 and len(t) == 1:
        # 始点 s[0], 終点 t[0] の有向オイラー路
        return True, s[0], t[0]
    else:
        # 有向オイラー路が存在しない
        return False, -1, -1


n, m = map(int, input().split())
graph = [[] for _ in range(n)]
for _ in range(m):
    a, b = map(int, input().split())
    graph[a].append(b)
    graph[b].append(a) 

judge, s, t = is_eulerian(graph)
if judge and s == -1 and t == -1:
    print("YES")
else:
    print("NO")