E

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    _test
    {
        int n;
        cin>>n;

        vector<ll int> a(n);
        for(auto &e: a)     cin>>e;

        int mmin = *min_element(a.begin(), a.end());

        int pos = -1;

        for(int i=0; i<n; i++)
        {
            if(a[i] == mmin)
            {
                pos = i;
                break;
            }
        }

        if(pos==n-1 || is_sorted(a.begin()+pos, a.end()))
            cout<<pos<<"\n";
        else
            cout<<-1<<"\n";
    }
}