ABC143 B - TAKOYAKI FESTIVAL 2019
https://atcoder.jp/contests/abc143/tasks/abc143_b
提出
code: python
import itertools
n = int(input())
d = list(map(int, input().split()))
ans = 0
for i in itertools.combinations(d, 2):
ans += i
0
* i
1
print(ans)
テーマ
#itertools