#include <iostream>
#include <iterator>
#include <vector>
 
 
std::vector<int> operator +(std::vector<int> lhs, std::vector<int> const& rhs) {
   lhs.insert(std::end(lhs), std::begin(rhs), std::end(rhs));
   return lhs;   
}
 
 
int main() {
   std::vector<int> const lhs {1, 2, 3};
   std::vector<int> const rhs {4, 5, 6};
 
   std::vector<int> const result = lhs + rhs;
 
   for (auto value : result) {
      std::cout << value << ' ';
   }
   std::cout << std::endl;
}
 

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