1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

//g++ -std=c++17 -Wshadow -Wall -fsanitize=address -fsanitize=undefined -D_GLIBCXX_DEBUG -g PROGRAM -o OUTPUT -DLOCAL -lasan -lubsan
#include <bits/stdc++.h>

#define ll long long
#define ull unsigned long long
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define eps 1e-6
#define pi 3.141592653589793
using namespace std;

typedef vector<int> VII;
typedef vector<ll> VLL;
typedef pair<int, int> PII;
typedef vector<pair<int, int>> VPII;
typedef vector<pair<int, PII>> VPPI;
const int MOD = 1e9 + 7;
const int INF = 1e9;


inline ll modulo(ll a, ll m)
{
    return (a % m + m) % m;
}

inline ll modInverse(ll a, ll m)
{
    assert(__gcd(a, m) == 1);
    ll m0 = m;
    ll y = 0, x = 1;

    if (m == 1)
        return 0;

    while (a > 1)
    {
        ll q = a / m;
        ll t = m;

        m = a % m, a = t;
        t = y;

        y = x - q * y;
        x = t;
    }

    if (x < 0)
        x += m0;

    return x;
}

inline ll modPow(ll x, ll y, ll m)
{ //x^y % m
    if (y == 0)
        return 1LL;
    else if (y == 1)
        return x;
    else
    {
        ll ans = modPow(x, y / 2, m) % m;
        if (y & 1)
        {
            return (((ans * ans) % m) * x) % m;
        }
        else
        {
            return (ans * ans) % m;
        }
    }
}

vector<string> split(char d,string s)
{
    stringstream ss(s);
    string t;
    vector<string> words;
    while(getline(ss,t,d))
    {
        words.pb(t);
    }

    return words;
}

int main(int argc, char *argv[])
{
    
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int t;
    cin >> t;
    while(t--){
        int n;
        cin >> n;
        VII arr(n);
        for(auto &x:arr)
            cin >> x;

        auto mx = *max_element(all(arr));
        if(count(all(arr),mx)==n)
            cout << "-1\n";
        else{
            arr.insert(arr.begin(), -1);
            arr.pb(-1);
            for (int i = 1; i < n; ++i)
            {
                if(arr[i]==mx && (arr[i-1]<mx || arr[i+1]<mx))
                {
                    cout << i << '\n';
                    break;
                }
            }
        }
    }

    return 0;
}
