import sys
input = sys.stdin.readline
n,m=map(int,input().split())
adj=[set() for _ in range(n)]
adj2=[set() for _ in range(n)]
from collections import defaultdict,deque

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

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

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

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

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        group_members = defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members

    def __str__(self):
        return '\n'.join(f'{r}: {m}' for r, m in self.all_group_members().items())

uf=UnionFind(n)
for _ in range(m):
  l=list(map(str,input().split()))
  a=int(l[0])-1
  b=int(l[2])-1
  if l[1]=="<==>":
    adj[a].add(b)
    adj[b].add(a)
  else:
    adj2[a].add(b)
    adj2[b].add(a)
  uf.union(a,b)
for i in range(n):
  for j in adj[i]:
    if j in adj2[i]:
      print("No")
      exit()
dist = [-1]*n
for i in range(n):
  if dist[i]!=-1:
    continue
  que = deque([i])
  dist[i] = 0
  while que:
    v = que.popleft()
    e = dist[v]
    for w in adj[v]:
      if dist[w] > -1:
        if dist[w]==1-e:
          print("No")
          exit()
      else:
        dist[w] = e
        que.append(w)
    for w in adj2[v]:
      if dist[w] > -1:
        if dist[w]==e:
          print("No")
          exit()
      else:
        dist[w] = 1-e
        que.append(w)  
ans=[]
for l in list(uf.all_group_members().values()):
  zero=[]
  one=[]
  for i in l:
    if dist[i]==0:
      zero.append(i+1)
    else:
      one.append(i+1)
  if len(zero)>=len(one):
    ans+=zero
  else:
    ans+=one
if len(ans)>=(n+1)//2:
  print("Yes")
  print(len(ans))
  ans.sort()
  print(*ans)
else:
  print("No")