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#include <iostream> #include <vector> #include <algorithm> using namespace std; int main(void) { int n; vector<int> stick; int totalLength = 0; long long answer = 0; ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0); cin >> n; stick.resize(n); for (int i = 0; i < n; i++) { cin >> stick[i]; totalLength += stick[i]; } sort(stick.begin(), stick.end()); for (int i = 0; i < n - 1; i++) { totalLength -= stick[i]; answer += stick[i] * totalLength; } cout << answer; return (0); }