#include<iostream>
#include<vector>
#include<algorithm>
#include<iterator>
using namespace std;
template <typename RandomIt>
pair<RandomIt, RandomIt> FindStartsWith(
	RandomIt range_begin, RandomIt range_end,
	char prefix) {
	pair<RandomIt, RandomIt>p;
	auto research = binary_search(range_begin, range_end,
	[prefix](const string& str) {
			return str[0] == prefix; });

	if (research == false) {
		auto position = upper_bound(range_begin, range_end,
			[prefix](const string& str) {
				return	static_cast<char>(str[0]) > prefix; });
		p.first = position;
		p.second = position;
		return p;
	}
	else {

		p.first = upper_bound(range_begin, range_end, prefix);
		p.second = lower_bound(range_begin, range_end, prefix) - 1;
		return p;
	}
}