cppreference.com > C++ Algorithms > copy_n copy_n Syntax:
      #include <algorithm>
      iterator copy_n( iterator from, size_t num, iterator to );
The copy_n() function copies num elements starting at from to the destination pointed at by to. To put it another way, copy_n() performs num assignments and duplicates a subrange. The return value of copy_n() is an iterator that points to the last element that was copied, i.e. (to + num). This function runs in linear time. Related topics: copy copy_backward swap