#include <bits/stdc++.h>
using namespace std;

using ll = long long;

bool chmin(auto &a, auto b) { return a > b ? a = b, true : false; }
bool chmax(auto &a, auto b) { return a < b ? a = b, true : false; }

void solve() {
    int K;
    string S;
    cin >> K >> S;
    if(K >= ssize(S) - 1) cout << string(ssize(S), S.front()) << endl;
    else cout << string(K, S.front()) + S.substr(0, ssize(S) - K) << endl;
}

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

    int T;
    cin >> T;
    while(T--) solve();
}