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

int main()
{
	std::vector<int> a{ 1, 2, 3, 4, 5 };
	std::vector<int> b{ 4, 5, 6, 7 };
	std::vector<int> c;

	std::set_difference(a.begin(), a.end(), b.begin(), b.end(), std::inserter(c, c.begin()));

	for (auto it : c)
	{
		std::cout << it << " ";
	}

	return 0;
}