F

#include <bits/stdc++.h>

using namespace std;

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

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

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

        if(is_sorted(a.begin(), a.end()))
        {
            cout<<0<<"\n";
            continue;
        }

        tmp = a;
        reverse(tmp.begin(), tmp.end());

        if(is_sorted(tmp.begin(), tmp.end()))
        {
            cout<<1<<"\n";
            continue;
        }

        int f = 0, y = -1, z = -1,cnt=0;

        auto helper = [&]()
        {
            int mmin = *min_element(a.begin(), a.end());
            int x;

            for(int i=0; i<n; i++)
            {
                if(a[i]==mmin && a[((i-1)+n)%n]>a[i])
                {
                    x = i;
                    break;
                }
            }

            if(!cnt)        y = x;
            else            z = x;

            int j = (x+1) % n;
            bool chk = 1;

            while(j!=x && chk)
            {
                chk &= (a[j] >= a[((j-1)+n)%n]);
                j++;
                j %= n;
            }

            cnt++;

            return chk;
        };

        auto cyclicSorted = [&]()
        {
            if(helper())        f ^= 1;
            reverse(a.begin(), a.end());
            if(helper())        f ^= 2;

            return f;
        };

        if(!cyclicSorted())
        {
            cout<<-1<<"\n";
            continue;
        }

        int ans = 1e9;

        if(f&1)     ans = min(ans, min(n-y, 2+y));
        if(f&2)     ans = min(ans, min(1+n-z, 1+z));

        cout<<ans<<"\n";
    }
}