template<class InputIterator, class Size, class Function>
constexpr InputIterator for_each_n(InputIterator first, Size n, Function f);

template<class ExecutionPolicy, class ForwardIterator, class Size, class Function>
ForwardIterator for_each_n(ExecutionPolicy&& exec, ForwardIterator first, Size n, Function f);

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

template<class T>
auto print(const std::vector<T>& v)
{
    for (auto c : v)
        std::cout << c << ' ';
}

int main()
{
    std::vector<int> vec{0,1,2,3,4,5,6,7,8,9};
    std::for_each_n(std::begin(vec), std::size(vec), [](auto& data) {
        data *= 10;
    });
    print(vec);
}

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