#include <bits/stdc++.h>
using namespace std;
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
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 WA_DEBUG
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

using ll  = long long;
using ull = unsigned long long;
#define pb push_back
#define fi first
#define se second
#define rep(i,a,b) for(int i=int(a);i<=(int)(b);i++)
#define per(i,a,b) for(int i=int(a);i>=(int)(b);i--)
const int mod  = 1e9+7;
const int inf  = 0x3f3f3f3f;
const int maxn = 1e5+10;
int main() {
#ifndef WA_DEBUG
    ios::sync_with_stdio(false);cin.tie(nullptr);
#endif
    int _;
    cin>>_;
    while(_--) {
        int n;
        cin>>n; 
        string a,b,c;
        cin>>a>>b>>c;
        int lena=0,lenb=0,lenc=0;
        rep(i,1,3*n) {
            vector<int> cnt(2,0);
            if(lena<2*n) cnt[a[lena]-'0']++;
            if(lenb<2*n) cnt[b[lenb]-'0']++;
            if(lenc<2*n) cnt[c[lenc]-'0']++;
            if(cnt[0]>cnt[1]) {
                cout<<0;
                if(lena<2*n&&a[lena]=='0') lena++;
                if(lenb<2*n&&b[lenb]=='0') lenb++;
                if(lenc<2*n&&c[lenc]=='0') lenc++;
            }
            else {
                cout<<1;
                if(lena<2*n&&a[lena]=='1') lena++;
                if(lenb<2*n&&b[lenb]=='1') lenb++;
                if(lenc<2*n&&c[lenc]=='1') lenc++;
            }
            if(lena==2*n||lenb==2*n||lenc==2*n) {
                break;
            }
        }
        if(lena==2*n) {
            if(lenb>lenc) {
                while(lenb<2*n) cout<<b[lenb++];
            }
            else {
                while(lenc<2*n) cout<<c[lenc++];
            }
        }
        else if(lenb==2*n) {
            if(lena>lenc) {
                while(lena<2*n) cout<<a[lena++];
            }
            else {
                while(lenc<2*n) cout<<c[lenc++];
            }
        }
        else {
            if(lena>lenb) {
                while(lena<2*n) cout<<a[lena++];
            }
            else {
                while(lenb<2*n) cout<<b[lenb++];
            }
        }
        cout<<'\n';
    }
    return 0;
}
