from collections import defaultdict
N = int(input())
p = []
count = defaultdict(int)
for _ in range(N):
    s,t = input().split()
    count[s] += 1
    count[t] += 1
    p.append((s,t))

for s,t in p:
    if(count[s] >= 2 and count[t] >= 2):
        print("No")
        exit()
print("Yes")