#include <bits/stdc++.h>
using namespace std;

void solve() {
	int N, K;
	cin >> N >> K;
	vector<int> digits(N);
	{
		string s;
		cin >> s;
		reverse(s.begin(), s.end());
		for (int i = 0; i < N; i++) {
			digits[i] = int(s[i] - '0');
		}
	}

	auto add = [&](vector<int> a, vector<int> b) -> vector<int> {
		int nsz = max(int(a.size()), int(b.size())) + 1;
		a.resize(nsz);
		int carry = 0;
		for (int i = 0; i < nsz; i++) {
			a[i] += (i < int(b.size()) ? b[i] : 0) + carry;
			carry = a[i] / 10;
			a[i] %= 10;
		}
		while (a.back() == 0) {
			a.pop_back();
		}
		return a;
	};

	auto test = [&](int mask) -> vector<int> {
		vector<int> diffs;
		int extra = 0;
		int r = 0;
		for (int z = 0; z < K; z++) {
			diffs.push_back((mask % 3) - 1);
			mask /= 3;
			r += diffs.back();
			extra += r;
		}
		if ((N - extra) % (K + 1) != 0) return {};

		int step = (N - extra) / (K + 1);
		int cur = 0;
		vector<int> cnd;
		for (int i = 0; i < K+1; i++) {
			if (step <= 0) return {};
			cnd = add(cnd, vector<int>(digits.begin() + cur, digits.begin() + (cur + step)));
			cur += step;
			if (i < K) {
				step += diffs[i];
			}
		}
		return cnd;
	};

	auto is_less = [&](const vector<int>& a, const vector<int>& b) -> bool {
		if (a.size() < b.size()) return true;
		if (a.size() > b.size()) return false;
		for (int i = int(a.size())-1; i >= 0; i--) {
			if (a[i] < b[i]) return true;
			if (a[i] > b[i]) return false;
		}
		return false;
	};

	int all = 1;
	for (int _ = 0; _ < K; _++) all *= 3;
	vector<int> ans;
	for (int mask = 0; mask < all; mask++) {
		auto cnd = test(mask);
		if (!cnd.empty() && (ans.empty() || is_less(cnd, ans))) {
			swap(ans, cnd);
		}
	}
	assert(!ans.empty());
	for (int i = int(ans.size())-1; i >= 0; i--) {
		cout << ans[i];
	}
	cout << '\n';
}

int main() {
	ios_base::sync_with_stdio(false), cin.tie(nullptr);

	int T;
	cin >> T;
	while (T--) solve();
}