#include <bits/stdc++.h>

[[nodiscard]] static inline constexpr std::string solve(const uint_fast32_t K, const std::string& S) noexcept
{
	if (K >= S.size())
		return std::string(S.size(), S.front());
	else
		return std::string(K, S.front()) + S.substr(0, S.size() - K);
}

int main()
{
	std::cin.tie(nullptr);
	std::ios::sync_with_stdio(false);
	
	uint_fast32_t T;
	std::cin >> T;
	for (uint_fast32_t i = 0; i < T; ++i)
	{
		uint_fast32_t K;
		std::string S;
		S.reserve(64);
		std::cin >> K >> S;

		std::cout << solve(K, S) << '\n';
	}

	return 0;
}