#include using namespace std; int main(){ int N; cin >> N; vector S(N); for(auto &x : S) cin >> x; unordered_set st; for(int i = 0; i < N; i++){ for(int j = i + 1; j < N; j++){ st.emplace(S[i] + S[j]); st.emplace(S[j] + S[i]); } } cout << st.size(); }