import sys;input=sys.stdin.readline
from collections.abc import Sequence
def MI():return map(int,input().split())
def PRINT(ans):
    if isinstance(ans,bool):
        s='Yes' if ans else 'No'
    elif isinstance(ans,Sequence) and not isinstance(ans,str):
        s='\n'.join(map(str,ans))
    else:
        s=str(ans)
    sys.stdout.write(s+'\n')
def PRINT1(seq):
    assert isinstance(seq,Sequence)
    sys.stdout.write(' '.join(map(str,seq)))
    sys.stdout.write('\n')
INF=10**18
mod=998244353
D4=[(1,0),(-1,0),(0,1),(0,-1)]
D8=D4+[(1,1),(-1,1),(1,-1),(-1,-1)]
#from math import gcd,lcm,log2,sqrt,isqrt
from collections import deque,defaultdict
#from heapq import heappop,heappush,heapify
#from bisect import bisect_left,bisect_right
#from itertools import permutations,combinations,combinations_with_replacement
#from functools import lru_cache
#from atcoder.dsu import DSU
#from atcoder.math import inv_mod

## main
N=int(input())
S=defaultdict(int)
l=[]
for i in range(N):
    s,t=input().split()
    l.append((s,t))
    S[s]+=1
    S[t]+=1
r=True
for s,t in l:
    if S[s]>1 and S[t]>1:
        r=False
        break
PRINT(r)