import sys; input = sys.stdin.readline
N, M = map(int, input().split())
G = [[] for _ in range(N)]
for _ in range(M):
    a, b = map(int, input().split())
    a -= 1; b -= 1
    G[a] += [b]; G[b] += [a]
T = 0; V = [0]*N; D = [-1]*N; L = [-1]*N; E = []
for i in range(N):
    if not V[i]:
        S = [(2*i, -1)]
        while S:
            vs, p = S.pop(); v, s = divmod(vs, 2)
            if s&1:
                L[v] = min(L[v], L[p])
                if L[p] > D[v]: print('NO'); exit()
                E.append((v, p))
            else:
                if V[v]: S.pop(); continue
                V[v] = 1; D[v] = L[v] = T; T += 1
                for to in G[v]:
                    if to == p: continue
                    if V[to]: L[v] = min(L[v], D[to]); E.append((v, to))
                    else: S.append((vs^1, to)); S.append((2*to, v))
print('YES')
for a, b in E: print(a+1, b+1)