// https://github.com/potato167/po167_library
#include <bits/stdc++.h>
#include <cassert>
using namespace std;
using ll=long long;
const ll ILL=2167167167167167167;
const int INF=2100000000;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using pq_ = priority_queue<T, vector<T>, greater<T>>;
template<class T> int LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> int UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(b<a){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
bool yneos(bool a,bool upp=false){if(a){cout<<(upp?"YES\n":"Yes\n");}else{cout<<(upp?"NO\n":"No\n");}return a;}
template<class T> void vec_out(vector<T> &p,int ty=0){
    if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
    else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(int)(a&1),a>>=1;}return res;}
template<class T> T square(T a){return a * a;}



void solve();
// DEAR MYSTERIES / TOMOO
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    cin >> t;
    rep(i, 0, t) solve();
}

void solve(){
    int N;
    cin >> N;
    vector<int> A(N);
    rep(i, 0, N) cin >> A[i];
    So(A);
    if (N == 1) {
        cout << A[0] << "\n";
        return;
    }
    vector<int> C(N);
    rep(i, 0, N) {
        if (A[i] < N) C[A[i]]++;
    }
    int l = 0, r = N + 1;
    while (r - l > 1) {
        int m = (l + r) / 2;
        int use = 0;
        int nec = 1;
        // cout << m << endl;
        for (int i = m - 1; i > 0; i--) {
            // cout << i << " " << use << " " << nec << " " << C[i] << endl;
            int tmp = min(nec, C[i]);
            use += tmp;
            nec += nec - tmp;
            if (nec > N) break;
        }
        if (nec + use <= N) l = m;
        else r = m;
    }
    cout << l << "\n";
}
/*
 * any -> 0
 * 0 -> 1
 * 0, 1 -> 2
 * 0, 1, 2 -> 3
 * 0, 1, 2, 3 -> 4
 * 二分探索が可能
 */