AtCoder Anfängerwettbewerb: D Problemantworten Python

import collections
 
N = int(input())
A = sorted(map(int, input().split()))
 
cnt = collections.defaultdict(int)
for a in A:
    cnt[a] += 1
ans = sum(A)
 
Q = int(input())
for _ in range(Q):
    B, C = map(int, input().split())
    ans += (C - B) * cnt[B]
    cnt[C] += cnt[B]
    cnt[B] = 0

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