#include <iostream> #include <vector> using namespace std; int main() { int n; cin >> n; vector<int> values(n); for (int i = 0; i < n; ++i) { cin >> values[i]; } long long totalContribution = 0; for (int i = 0; i < n; ++i) { for (int j = i + 1; j < n; ++j) { for (int k = j + 1; k < n; ++k) { totalContribution += values[i] + values[j] + values[k]; } } } cout << totalContribution << endl; return 0; }