#include #include using namespace std; using namespace atcoder; typedef int64_t lint; #define rep(i, n) for(int i=0; i; using vvi = vector>; template inline void vin(vector& v) { rep(i, v.size()) cin >> v.at(i); } template inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } template inline void drop(T x) { cout << x << endl; exit(0); } template void vout(vector v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; } constexpr lint LINF = LLONG_MAX/2; int main() { lint N; cin >> N; vi v(N); vin(v); lint a=0, b=0, c=0, x, y, z; vi w(10); rep(i, N) w[v[i]]++; repx(i, 1, 9) { repx(j, 1, 9) { a = pow(i, j); b += a*w[i]*w[j]; } } cout << b << endl; }