#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
#include <chrono>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t;
cin>>t;
while (t--){
int n, ans, c=0;
cin>>n;
vector<int> vect(n+1);
for (int i=1; i<=n; ++i)cin>>vect[i];
for (int i=1; i<=n; ++i){
bool can=1;
vector<bool> visited(n+1, 0);
visited[vect[1]]=1;
for (int j=1, p=1; j<=n; ++j){
if (i==j)continue;
++p;
if (!visited[j]&&vect[p]!=j)can=0;
visited[vect[p]]=1;
}
if (can)++c, ans=i;
}
if (c>1)cout<<"0\n";
else cout<<ans<<"\n";
}
}
