from collections import Counter

N=int(input())

A=[input().split() for i in range(N)]

flag=1

for i in range(N):
    a,b=A[i]

    for j in range(N):
        if i!=j:
            c,d=A[j]

            if (a==c or a==d) and (b==c or b==d):
                flag=0
if flag:
    print("Yes")
else:
    print("No")