from collections import deque

N, M = map(int, input().split())
G = [[] for _ in range(N)]
for _ in range(M):
    u, E, v = input().split()
    u, v = int(u)-1, int(v)-1
    if E == "<==>":
        G[u].append((v, 0))
        G[v].append((u, 0))
    else:
        G[u].append((v, 1))
        G[v].append((u, 1))

visited = [-1]*N
ans = []
for i in range(N):
    if visited[i] == -1:
        visited[i] = 0
        que = deque()
        que.append(i)
        zero = [i]
        one = []
        while que:
            n = que.popleft()
            for v, c in G[n]:
                if visited[v] == -1:
                    visited[v] = (visited[n]+c)%2
                    que.append(v)
                    if visited[v] == 0:
                        zero.append(v)
                    else:
                        one.append(v)
                elif visited[v] != (visited[n]+c)%2:
                    exit(print("No"))
        if len(zero) >= len(one):
            ans += zero
        else:
            ans += one

print("Yes")
print(len(ans))
print(*[i+1 for i in sorted(ans)])