#include <iostream>
#include <cstring>
using namespace std;
int f[1000001];
 
int solve (int a[], int n) {
	for (int i=0; i<n; i++) {
		if (a[i]>=0 && !f[a[i]]) {
			f[a[i]]=1;
		} 
	}
	for (int i=1; i<1000000; i++) {
		if (!f[i]) return i; 
	}
	return -1;
}
 
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int t; cin >> t;
    while (t--) {
    	memset (f, sizeof(f), 0);
	    int n; cin >> n;
	    int a[n]; 
	    for (int i=0; i<n; i++) cin >> a[i]; 
		cout << solve (a, n) << endl;
	}
}

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