B

#include <bits/stdc++.h>

using namespace std;

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

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

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

        if(*max_element(a.begin(), a.end()) ==
           *min_element(a.begin(), a.end()))
        {
            cout<<"-1\n";
            continue;
        }

        int ans=n, cnt=0;

        for(int i=0; i<n; i++)
        {
            if(a[0] == a[i])        cnt++;
            else
            {
                ans = min(ans, cnt);
                cnt = 0;
            }
        }

        ans = min(ans, cnt);

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