import sys


def deepFirstSearch(V, i, distance):
    for j in range(len(V[i][1])):
        vertex = V[i][1][j]
        if V[vertex - 1][0] == 0:
            V[vertex - 1][0] = 2
            V[vertex - 1][2] = distance + 1
            deepFirstSearch(V, vertex - 1, distance + 1)


def isBipartite(V, E):
    for i in range(len(V)):
        if V[i][0] == 0:
            V[i][0] = 1
            deepFirstSearch(V, i, 0)

    for i in range(len(E)):
        v1, v2 = E[i]
        if V[v1 - 1][2] % 2 == V[v2 - 1][2] % 2:
            return 'NO'
    return 'YES'


reader = sys.stdin
vertexCount, edgesCount = tuple(map(int, next(reader).strip().split()))
V = []
E = []
for i in range(vertexCount):
    V.append([0, [], 0])
for i in range(edgesCount):
    v1, v2 = tuple(map(int, next(reader).strip().split()))
    E.append((v1, v2))
    V[v1 - 1][1].append(v2)
    V[v2 - 1][1].append(v1)

print(isBipartite(V, E))