#if defined(LOCAL)
#define _GLIBCXX_DEBUG
#else
#define NDEBUG
#endif

#include <bits/stdc++.h>

#if defined(LOCAL)
#define DBG_MACRO_NO_WARNING
#include <dbg.hpp>
#else
#define dbg(x...) (0)
#endif

using namespace std;

using ll = long long;

// #define int ll
#define rep(i, f, t) for (int i = (f), ed##i = (t); i <= ed##i; ++i)
#define re(i, t) rep (i, 1, t)
#define per(i, t, f) for (int i = (t), ed##i = (f); i >= ed##i; --i)
#define ste(i, f, t, s) for (int i = (f), ed##i = (t); i <= ed##i; i += s)
#define nxt(i, f, g) for (int i = g.h[f]; i; i = g.e[i].n)
#define umod(x) ((x) >= mo && ((x) -= mo))
#define dmod(x) ((x) < 0 && ((x) += mo))
#define y1 y1__
#define fio(x) (freopen(x ".in", "r", stdin), freopen(x ".out", "w", stdout))

template <class T, class E>
__attribute__((always_inline)) inline void up(T &x, E &&y) {
  if (x < y) x = y;
}
template <class T, class E>
__attribute__((always_inline)) inline void down(T &x, E &&y) {
  if (y < x) x = y;
}

const int N = 2e6 + 9;
int n, m, a[N], ans1[N], ans2[N];
vector<int> one;

inline bool Ck(int len1, int len2, int p) {
  int dif = len2 - (len1 - 1);
  int onecnt = one.end() - upper_bound(one.begin(), one.end(), p);
  if (onecnt < dif) return 0;
  int np = *(lower_bound(one.begin(), one.end(), p) + dif);
  int zerocnt = np - p - dif;
  if (zerocnt > len1 - 1) return 0;
  return 1;
}

inline void Work() {
  cin >> n >> m;
  if (n < m) swap(n, m);
  one.clear();
  re (i, n + m) {
    char c;
    cin >> c;
    a[i] = c - '0';
    if (a[i] == 1) one.push_back(i);
  }
  rep (i, 0, n + m + 1) ans1[i] = ans2[i] = 0;
  int hd1 = 0, hd2 = n - m;
  re (i, n + m) {
    if (a[i] == 0) {
      if (hd1 == n)
        ans2[++hd2] = 0;
      else if (hd2 == n)
        ans1[++hd1] = 0;
      else if (hd1 > hd2)
        ans1[++hd1] = 0;
      else
        ans2[++hd2] = 0;
      continue;
    }
    if (hd1 == n)
      ans2[++hd2] = 1;
    else if (hd2 == n)
      ans1[++hd1] = 1;
    else if (hd1 >= hd2) {
      if (Ck(n - hd1, n - hd2, i))
        ans1[++hd1] = 1;
      else
        ans2[++hd2] = 1;
    } else {
      if (Ck(n - hd2, n - hd1, i))
        ans2[++hd2] = 1;
      else
        ans1[++hd1] = 1;
    }
  }
  assert(hd1 == n);
  assert(hd2 == n);
  // dbg(hd1, hd2);
  // re (i, n) cerr << ans1[i];
  // cerr << '\n';
  // re (i, n) cerr << ans2[i];
  // cerr << '\n';
  per (i, n, 1) {
    ans1[i] += ans2[i], ans1[i - 1] += ans1[i] >> 1, ans1[i] &= 1;
  }
  rep (i, 0, n) {
    if (ans1[i]) {
      rep (j, i, n) cout << ans1[j];
      cout << '\n';
      return;
    }
  }
  cout << "0\n";
}

signed main() {
  // fio("partition");
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int T;
  cin >> T;
  while (T--) Work();
  return 0;
}