#include #include #define OVERLOAD_REP(_1, _2, _3, name, ...) name #define REP1(i,n) for (auto i = std::decay_t{}; (i) != (n); ++(i)) #define REP2(i,l,r) for (auto i = (l); (i) != (r); ++(i)) #define rep(...) OVERLOAD_REP(__VA_ARGS__, REP2, REP1)(__VA_ARGS__) #define all(a) (a).begin(),(a).end() #define rall(a) (a).rbegin(),(a).rend() using namespace std; using namespace atcoder; using ll = long long; using ull = unsigned long long; using P = pair; using LP = pair; using SP = pair; using vi = vector; using vl = vector; using vs = vector; using vc = vector; using mint1 = modint1000000007; using mint9 = modint998244353; const int INF = 2e9; const long long LINF = 4e18; const int di[] = {0,1,0,-1,-1,1,-1,1}; const int dj[] = {1,0,-1,0,1,1,-1,-1}; template inline bool chmin(T& a, T b){if(a>b){a=b;return true;}return false;} template inline bool chmax(T& a, T b){if(a> n; vector a(n); rep(i , n) cin >> a[i]; rep(i , n) cnt[a[i]]++; long long res = 0; rep(i , n) { long long p = a[i]; rep(j , 1 , 9) { res += p*cnt[j]; p *= a[i]; } } cout << res << endl; return 0; }