n,m = map(int,input().split())
adj = [[] for _ in range(n)]
ban = [[] for _ in range(n)]
g = [0]+[-1]*(n-1); st = [0]
for _ in range(m):
    i,e,j = input().split()
    i,j = int(i)-1,int(j)-1
    if e=="<==>": adj[i].append(j); adj[j].append(i)
    else: ban[i].append(j); ban[j].append(i)
while st:
    p = st.pop()
    for c in adj[p]:
        if g[c]==-1: g[c] = g[p]; st.append(c)
        elif g[c]!=g[p]: exit(print("No"))
    for c in ban[p]:
        if g[c]==-1: g[c] = g[p]^1; st.append(c)
        elif g[c]==g[p]: exit(print("No"))
a = [i+1 for i in range(n) if g[i]==0]
b = [i+1 for i in range(n) if g[i]==1]
print("Yes"); print(max(len(a),len(b)))
print(*a if len(b)<=n//2 else b)