#include <bits/stdc++.h>   using namespace std;   const long long N = 112, INF = 1e18;   long long t, n, m, a[N];   long long B10(string s) {     reverse(s.begin(), s.end());     long long ret = 0;     for (long long i = 0; i < s.size(); i++) {       if (s[i] ==  1 ) ret += (1ll << i);     }     return ret;   }   string B2(long long a) {     string ret;     for (long long i = 0; i < m; i++) {       if (a & (1ll << i))         ret +=  1 ;       else         ret +=  0 ;     }     reverse(ret.begin(), ret.end());     return ret;   }   long long BS() {     long long low = 0, high = (1ll << m);     while (high - low > 1) {       long long mid = (low + high) >> 1;       long long v1 = mid - (lower_bound(a, a + n, mid) - a);       long long v2 = ((1ll << m) - n - 1) / 2;       if (v1 <= v2)         low = mid;       else         high = mid;     }     return low;   }   int32_t main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     cin >> t;     while (t--) {       cin >> n >> m;       for (long long i = 0; i < n; i++) {         string s;         cin >> s;         a[i] = B10(s);       }       sort(a, a + n);       cout << B2(BS()) <<   n ;     }     return 0;   }   