#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (int i = a; i < (b); i++)
#define Rep(i, a, b) for (int i = a; i >= (b); i--)
#define pb push_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define fi first
#define se second
#define SZ(x) (int)(x.size())
#define lowbit(x) ((x) & -(x))
using db = double;
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using pii = pair<int, int>;
using i128 = __int128_t;
// Think twice, code once

void solve() {
    int h; cin >> h;
    int n = (1 << h + 1) - 1;
    vi a(n + 1);
    rep(i, 2, n + 1) cin >> a[i];
    vi val(n + 1);
    rep(i, 2, n + 1) val[i] = val[i >> 1] + a[i];
    auto lca = [&](int u, int v) {
        while (u != v) u >>= 1, v >>= 1;
        return u;
    };
    vi tag(n + 1), vis(n + 1);
    vvi son(n + 1);
    rep(i, 1 << h, 1 << h + 1) {
        rep(j, i + 1, 1 << h + 1) {
            int k = lca(i, j);
            tag[k] += (val[i] == val[j]);
        }
        son[i].pb(i);
    }
    int tot = 0;
    Rep(l, h - 1, 0) {
        tot++;
        rep(i, 1 << l, 1 << l + 1) {
            if (tag[i]) {
                if (!tot--) { cout << -1 << endl; return; }
                for (auto u : son[i << 1]) {
                    assert(!vis[u]);
                    vis[u] = 1;
                    rep(v, 1 << h, 1 << h + 1) if (!vis[v]) {
                        int w = lca(u, v);
                        tag[w] -= (val[u] == val[v]);
                    }
                }
                son[i << 1].clear();
            }
            assert(!tag[i]);
            for (auto u : son[i << 1]) son[i].pb(u);
            for (auto u : son[i << 1 | 1]) son[i].pb(u);
        }
    }
    cout << h - tot << endl;
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
    int T = 1;
    cin >> T;
    while (T--) solve();
    return 0;
}