#include <bits/stdc++.h>


using namespace std;

template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
 void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#ifdef ONPC
  #define deb(...) cerr << '[' << __FILE__ << ':' << __LINE__ << "] (" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
  #pragma GCC optimize("O3,unroll-loops")
  #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
  #define deb(...)
#endif

// c++ short types
#define vt vector
//typedef long long ll;
typedef long double ld;

void whattime() { cout << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl; }
// const int mod = 1e9 + 7;
const int mod = 998244353;
const int inf = 1e9;
const int64_t infll = 1e13;
bool debug = false;
const ld eps = 1e-9;
const ld pi = acos(-1);
mt19937_64 rng((int) chrono::steady_clock::now().time_since_epoch().count());

const int maxn = 2e5, K = 10;
int subvalue[maxn][K];

struct num {
  const int base = 1000'000'000;
  vt<int> elems;
  num(int x = 0) {
    elems = {x};
  }
  num(int l, int r) {
    for(int i = l; i <= r; i += 9) {
      elems.push_back(subvalue[i][min(9, r-i+1)]);
    }
    if(elems.empty()) {
      elems = {0};
    }
  }
  void asd() {
    while(not elems.size() > 1 and elems.back() == 0) {
      elems.pop_back();
    }
    if(elems.empty()) {
      elems.push_back(0);
    }
  }
  void add(num &b) {
    int carry = 0;
    for(int i = 0; i < max(elems.size(), b.elems.size()) || carry > 0; ++i) {
      if(elems.size() == i) {
        elems.push_back(0);
      }
      elems[i] += carry + (i < b.elems.size() ? b.elems[i] : 0);
      carry = elems[i] >= base;
      if(carry) {
        elems[i] -= base;
      }
    }
  }
  void print() {
    asd();
    for(int i = elems.size() - 1; i >= 0; --i) {
      cout << elems[i];
    }
    cout << '\n';
  }
};

bool cmp(num &a, num &b) {
  a.asd();
  b.asd();
  if(a.elems.size() != b.elems.size()) {
    return a.elems.size() < b.elems.size();
  }
  for(int i = a.elems.size()-1; i>=0; --i) {
    if(a.elems[i] != b.elems[i]){
      return a.elems[i] < b.elems[i];
    }
  }
  return false;
}

void solve() {
  int n, k;
  cin >> n >> k;
  string s; cin >> s;
  for(int i = 0; i < n; ++i) {
    for(int j = 1; j < K; ++j) {
      subvalue[i][j] = stoi(s.substr(i, j));
    }
  }
  int z = n / (k+1);
  num res(0, s.size()-1);
  auto Dfs = [&](auto self, int id, int lastLength, int total, num val = 0) -> void {
    if(!cmp(val, res)) {
      return ;
    }
    if(id == k + 1 || total >= n) {
      if(id == k + 1 and total == n ){
        deb(id, total, val.elems);
        swap(res.elems, val.elems);
      }
      return ;
    }
    for(auto delta: {-1, 0, +1}) {
      int nlength = lastLength + delta;
      if(nlength > 0) {
        num tmp = {0};
        tmp.elems = val.elems;
        num addend = {total, total + lastLength - 1};
        tmp.add(addend);
        self(self, id + 1, nlength, total + nlength, tmp);
      }
    }
  };
  for(auto x: {z-1,z, z+1}) if(x > 0) {
    Dfs(Dfs, 1, x, x, {0, x-1}); 
  }
  res.print();
}

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

	int tt = 1;;
	if(debug) {
		tt = 1e3;
	} else {
		cin >> tt;
	}

	for(int t = 0; t < tt; ++t) {
		solve();
	}
	
#ifdef ONPC
	whattime();
#endif
	
	return 0;
}