n = int(input())
S = [list(map(str, input().split())) for _ in range(n)]
from collections import defaultdict
dict = defaultdict(int)
for l, r in S:
    dict[l] += 1
    dict[r] += 1

for l, r in S:
    if dict[l] > 1 and dict[r] > 1:
        break
else:
    print("Yes")
    exit()
print("No")