#include<iostream>
#include<vector>
using namespace std;
int t;
int main(){
    cin >> t;
    while (t--){
        int n; cin >> n; int m = 1e9;
        vector <int> pos(n + 1, 0);
        vector <int> num(n + 1, 0);
        for (int i = 1; i < n + 1; ++i){
            int x; cin >> x;
            num[x]++;
            if (num[x] > 1){
                m = min(m, i - pos[x] + 1);
            }
            pos[x] = i;
        }
        if (n!= 1 && m != 1e9) cout << m << endl;
        else cout << -1 << endl;

    }
}