import sys

sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 63)
md = 10**9+7
# md = 998244353

n, m = LI()
to = [[] for _ in range(n)]

for _ in range(m):
    i, e, j = SI().split()
    i = int1(i)
    j = int1(j)
    c = len(e) == 5
    to[i].append((j, c))
    to[j].append((i, c))

def dfs(u):
    uu[color[u]].append(u+1)
    for v, c in to[u]:
        if color[v] == -1:
            color[v] = color[u] ^ c
            if dfs(v): return True
        elif color[v]!=color[u]^c:
            return True
    return False

color = [-1]*n
ans = []
for u in range(n):
    if color[u] != -1: continue
    color[u] = 0
    uu = [[], []]
    if dfs(u):
        print("No")
        exit()
    if len(uu[0])>len(uu[1]):
        ans+=uu[0]
    else:
        ans+=uu[1]
    # print(color)
    # print(uu)

ans.sort()
print("Yes")
print(len(ans))
print(*ans)