import sys
sys.setrecursionlimit(10**7)
def input():
    return sys.stdin.readline().strip()

def main():
    N = int(input())
    ST = []
    for _ in range(N):
        ST.extend(input().split())
    
    names = {}
    for s in ST:
        names[s] = names.get(s, 0) + 1
    
    for i in range(N):
        if names[ST[2*i]] != 1 and names[ST[2*i+1]] != 1:
            print('No')
            return
    print('Yes')

if __name__ == '__main__':
    main()