template<input_iterator I, weakly_incrementable O>
requires indirectly_copyable<I, O>
constexpr ranges::copy_n_result<I, O>
    copy_n(I first, iter_difference_t<I> n, O result);

#include <algorithm>
#include <iostream>
#include <string>
#include <vector>

namespace ranges = std::ranges;


int main()
{
    std::string copyed = "world!";
    std::vector<char> result {'h', 'e', 'l', 'l', 'o', ' '};

    ranges::copy_n(copyed.begin(), 5, std::back_inserter(result));

    for (auto c : result)
        std::cout << c;
    std::cout << std::endl;
}

hello world