C++ akinator

#include <iostream>
#include <iomanip>
#include <fstream>
#include <filesystem>

#include "nlohmann/json.hpp"

int main() {
	// Default file content: {"This are big":["Whale", "Cat"]}
	std::ifstream input("D://input.txt");

	nlohmann::json j;
	input >> j;
	input.close();

	auto question = j.begin();
	char resp;
	while (true) {
		std::cout << question.key() << "? (y/n)" << std::endl;
		std::cin >> resp;

		auto& answer = question.value()[resp == 'y' ? 0 : 1];
		if (answer.is_object()) {
			question = answer.begin();
			continue;
		}
		else {
			std::cout << answer.get<std::string>() << std::endl
				<< "That's right? (y/n)" << std::endl;
			std::cin >> resp;
			if (resp == 'y') {
				std::cout << "Cool!" << std::endl;
				return 0;
			}
			else {
				std::cin.ignore();
				std::string a, b, c = answer.get<std::string>();
				std::cout << "What did you think?" << std::endl;
				std::getline(std::cin, a);

				std::cout << "How does it differ from " << c << '?' << std::endl;
				std::getline(std::cin, b);

				std::cout << "OK, I'll remember this!" << std::endl;

				answer = { {b, {a, c}} };
			}
			break;
		}
	}

	std::ofstream output("D://input.txt.tmp");
	output << j;
	output.close();
	std::filesystem::rename("D://input.txt.tmp", "D://input.txt");

	system("pause");
	return 0;
}