from collections import defaultdict
N=int(input())
S=[]
T=[]
ST=defaultdict(int)
for _ in range(N):
    s,t=input().split()
    S.append(s)
    T.append(t)
    ST[s]+=1
    ST[t]+=1
for s,t in zip(S,T):
    if ST[s]>=2 and ST[t]>=2:
        exit(print("No"))
print("Yes")