#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int findWinner(int n, int arr[]) {
int map[1000]={0};
int no=n/2;
for(int i=0;i<n;i++){
map[arr[i]]++;
}
int maxn=arr[0];
int max=map[arr[0]];
for(int i=0;i<n;i++){
if(max<map[arr[i]]){
max=map[arr[i]];
maxn=arr[i];
}
}
if(max<n)return -1;
else return maxn;
}
int main() {
int t;
if (!(cin >> t)) return 0;
while (t--) {
int n;
if (!(cin >> n)) break;
int* arr = new int[n];
for (int i = 0; i < n; i++) {
cin >> arr[i];
}
cout << findWinner(n, arr) << endl;
delete[] arr;
}
return 0;
}
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