#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define x first
#define y second

using namespace std;

typedef long double ld;
typedef long long ll;

const ll MOD = (ll) 1e18;

vector <ll> answer, current;
string s;

void add_val(ll x, int pos)
{
	current[pos] += x;
	while (current[pos] >= MOD)
	{
	 	current[pos + 1]++;
	 	current[pos] -= MOD;
	 	pos++;
 	}
 	return;
}

void substr_val(ll x, int pos)
{
 	current[pos] -= x;
 	while (current[pos] < 0)
 	{
 	 	current[pos + 1]--;
 	 	current[pos] += MOD;
 	 	pos++;
 	}
 	return;
}

void rec_gen(int pos, int n, int ost, int bound)
{
 	if (ost == 0)
 	{
 		if ((int) current.size() < (int) answer.size()) answer = current;
 		else if ((int) current.size() == (int) answer.size())
 		{
 		 	int fl = 0;
 		 	for (int i = (int) current.size() - 1; i >= 0; i--)
 		 	{
 		 	 	if (current[i] < answer[i]) fl = 1;
 		 	 	if (current[i] > answer[i]) fl = -1;
 		 	 	if (fl != 0) break;
 		 	}
 		 	if (fl == 1) answer = current;
 		}
 		return; 	
 	}

 	int start = max(1, n - pos - bound * (ost - 1));
 	int finish = min(bound, n - pos);
 	if (start > finish) return;
 	
 	ll step = 1;
 	int num = 0;
 	for (int i = 1; i < start; i++)
 	{
 	 	int c = s[pos + i - 1] - '0';
 	 	add_val(c * step, num);
 	 	step *= 10;
 	 	if (step == MOD) step = 1, num++;
 	}
 	
 	for (int i = start; i <= finish; i++)
 	{
 	 	int c = s[pos + i - 1] - '0';
 	 	add_val(c * step, num);
 	 	
 	 	rec_gen(pos + i, n, ost - 1, bound);
 	 	
 	 	step *= 10;
 	 	if (step == MOD) step = 1, num++;
 	}

 	step = 1;
 	num = 0;
 	for (int i = 1; i <= finish; i++)
 	{
 	 	int c = s[pos + i - 1] - '0';
 	 	substr_val(c * step, num);
 	 	step *= 10;
 	 	if (step == MOD) step = 1, num++;
 	}
 	return;
}

void print()
{
 	while (answer.back() == 0) answer.pop_back();
 	for (int i = (int) answer.size() - 1; i >= 0; i--)
 	{
 	 	string s = to_string(answer[i]);
 	 	string t = string(18 - (int) s.length(), '0');
 	 	string res = (i == (int) answer.size() - 1) ? s : t + s;
 	 	cout << res;
 	}
 	cout << '\n';
}

int main()
{
 	//freopen("input.txt", "r", stdin);
 	//freopen("output.txt", "w", stdout);
	ios_base::sync_with_stdio(0); cin.tie(0);

	int test;
	cin >> test;
	for (int rep = 1; rep <= test; rep++)
	{
	 	int n, k;
	 	cin >> n >> k;

	 	cin >> s;
	 	reverse(s.begin(), s.end());

	 	int bound = (n - 1) / (k + 1) + 2;
	 	answer.clear(), current.clear();
	 	answer.resize(bound, MOD - 1), current.resize(bound, 0);
	 	rec_gen(0, n, k + 1, bound);

	 	print();
	}

	return 0;
}