#pragma GCC optimize ("O2")
#pragma GCC target ("avx")
//#include<bits/stdc++.h>
#include<iostream>
#include<cstring>
//#include<atcoder/all>
//using namespace atcoder;

using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep1(i, n) for(int i = 1; i <= (n); i++)
#define co(x) cout << (x) << "\n"
#define cosp(x) cout << (x) << " "
#define ce(x) cerr << (x) << "\n"
#define cesp(x) cerr << (x) << " "
#define pb push_back
#define mp make_pair
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define Would
#define you
#define please

char cn[1200010];
char* ci = cn, * di = cn, ct;
char tc[200002], *d1 = tc + 100000, *d2 = tc + 200000;
const char d[2] = "0";

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	rep(i, 100000) tc[i] = '0';
	rep(i, 100000) d1[i] = '1';
	d2[0] = '0';
	d2[1] = '\n';
	fread(cn, 1, 1200010, stdin);
	int T = 0;
	while ((ct = *ci++) >= '0') T = T * 10 + ct - '0';

	rep(t, T) {
		int N = 0;
		while ((ct = *ci++) >= '0') N = N * 10 + ct - '0';
		memcpy(di, d1 - N, N);
		di += N;
		memcpy(di, d2 - N, N + 2);
		di += N + 2;
		ci += 6 * N + 3;
	}
	fwrite(cn, 1, di - cn, stdout);

	Would you please return 0;
}
#include <bits/stdc++.h>

#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define endl "\n"
#define rep(i,n) repi(i,0,n)
#define repi(i,a,n) for(ll i=a;i<(ll)n;++i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define Show(val) cout<<(val)<<" "
#define Showln(val) cout<<(val)<<endl

using namespace std;
using ll = long long;
using P = pair<ll, ll>;
// using P = pair<int, int>;
void YN(bool a) { cout << (a ? "Yes" : "No"); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

void solve()
{
  ll t;
  cin >> t;
  
  rep(tt,t){
    ll n;
    string s;
    cin >> n >> s>>s>>s;
    s = string(n, '0')+string(n,'1')+'0';
    Showln(s); 
  }
}

int main()
{
  fastio;
  solve();

  return 0;
}