#include <iostream>
#include <vector>
using namespace std;
using ll=long long;
int main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	int ttt;
	cin>>ttt;
	while(ttt--){
		int n;
		cin>>n;
		vector<int> p(n);
		for(int i=0;i<n;i++)cin>>p[i];
		int l=-1;
		for(int i=0;i<n;i++){
			if(p[i]==1){
				if(n%4==2)l=(i+n-n/4)%n;
				else{
					if(p[(i+1)%n]<p[(i+n-1)%n]){
						l=(i+n-n/4+1)%n;
					}else{
						l=(i+n-n/4)%n;
					}
				}
			}
		}
		int f=0;
		if(p[l]>p[(l+n/2-1)%n])f^=1;
		if(p[(l+n/2)%n]>p[(l+n-1)%n])f^=1;
		if(f)cout<<(l+n/2)%n<<endl;
		else cout<<l<<endl;
	}
}