#include <iostream>
#include <locale>
 
struct phone_formatter : std::numpunct<char> {
	char do_thousands_sep() const override { return '-'; }
	std::string do_grouping() const override { return std::string({2, 2, 0}); }
};
 
int main() {
	std::locale loc(std::cout.getloc(), new phone_formatter);
	std::cout.imbue(loc);
	std::cout << 1234 << "\n";
	std::cout << 1234567 << "\n";
	std::cout << 123456789 << "\n";
    std::cout << 12 << "\n";
	return 0;
}

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