-     #include <iostream> 
-     #include <vector> 
-   
-     int main() { 
-     	std::vector<float> v{1,2,3,4,5}; 
-   
-         // Output: 3 
-     	std::cout << v.at(v.size()/2) << std::endl; 
-   
-         // Now a user provides another value, maybe 
-         v.push_back(6); 
-   
-         // Output: 4 
-     	std::cout << v.at(v.size()/2) << std::endl; 
-     } 
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