template<unsigned n>
struct Get {
 template<class X, class…Xs>
 constexpr auto operator()(X x, Xs…xs) {
   if constexpr(n > sizeof…(xs) ) {
     return;
   } else if constexpr(n > 0) {
     return Get<n-1>{}(xs…);
   } else {
     return x;
   }
 }
};