N = int(input())
G = {}
for _ in range(N):
    a,b = input().split()
    if a not in G:
        G[a] = [[],[]]
    G[a][1].append(b)
    if b not in G:
        G[b] = [[],[]]
    G[b][0].append(a)
for a in G:
    if len(G[a][1])==0:
        print(a)