//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
//#pragma GCC optimize("Ofast,fast-math")
//#pragma GCC target("avx,avx2")
//#pragma GCC optimize(2)
//#pragma GCC optimize(3)
//#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
//#define int long long
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef double db;
#define F(i, a, b) for(int i = a; i <= (b); ++i)
#define F2(i, a, b) for(int i = a; i < (b); ++i)
#define dF(i, a, b) for(int i = a; i >= (b); --i)
template<typename T> void debug(string s, T x) {
	cerr << "[" << s << "] = [" << x << "]\n";
}
template<typename T, typename... Args> void debug(string s, T x, Args... args) {
	for (int i = 0, b = 0; i < (int)s.size(); i++) if (s[i] == '(' || s[i] == '{') b++;
	else if (s[i] == ')' || s[i] == '}') b--;
	else if (s[i] == ',' && b == 0) {
		cerr << "[" << s.substr(0, i) << "] = [" << x << "] | ";
		debug(s.substr(s.find_first_not_of(' ', i + 1)), args...);
		break;
	}
}
#ifdef orzz
#define Debug(...) debug(#__VA_ARGS__, __VA_ARGS__)
#else
#define Debug(...)
#endif
#define pb push_back
#define fi first
#define se second
#define Mry fprintf(stderr, "%.3lf MB\n", (&Med - &Mbe) / 1048576.0)
#define Try cerr << 1e3 * clock() / CLOCKS_PER_SEC << " ms\n";
typedef long long ll;
// namespace Fread {const int SIZE = 1 << 17; char buf[SIZE], *S, *T; inline char getchar() {if (S == T) {T = (S = buf) + fread(buf, 1, SIZE, stdin); if (S == T) return '\n';} return *S++;}}
// namespace Fwrite {const int SIZE = 1 << 17; char buf[SIZE], *S = buf, *T = buf + SIZE; inline void flush() {fwrite(buf, 1, S - buf, stdout), S = buf;} inline void putchar(char c) {*S++ = c;if (S == T) flush();} struct NTR {~NTR() {flush();}} ztr;}
// #ifdef ONLINE_JUDGE
// #define getchar Fread::getchar
// #define putchar Fwrite::putchar
// #endif
inline int ri() {
	int x = 0;
	bool t = 0;
	char c = getchar();
	while (c < '0' || c > '9') t |= c == '-', c = getchar();
	while (c >= '0' && c <= '9') x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();
	return t ? -x : x;
}
inline void wi(int x) {
	if (x < 0) {
		putchar('-'), x = -x;
	}
	if (x > 9) wi(x / 10);
	putchar(x % 10 + 48);
}
inline void wi(int x, char s) {
	wi(x), putchar(s);
}
bool Mbe;
// mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int mod = 998244353;
const int inf = 0x3f3f3f3f;
const ll infll = 0x3f3f3f3f3f3f3f3f;
const int _ = 2e5 + 5;

int n, a[_], W;

bool fg[_];

int find_edge() {
	dF(i, n - 1, 0) {
		// [2^i,2^{i+1}-1]
		F(j, (1 << i), (1 << (i + 1)) - 1) if(!fg[j << 1] && !fg[j << 1 | 1] ){
			unordered_map<int, int> mp;
			function<void(int, int)> dfs = [&](int u, int nw) -> void {
//				Debug("1", j, u, nw);
				if(u >= W && u <= W + W - 1) {
					mp[nw]++;
					return;
				}
				if(fg[u]) return;
				dfs(u << 1, nw + a[u << 1]), dfs(u << 1 | 1, nw + a[u << 1 | 1]);
			};
			bool flg = 0;
			function<void(int, int)> dfs2 = [&](int u, int nw) -> void {
//					Debug(j, u, nw);
				if(u >= W && u <= W + W - 1) {
					if(mp.find(nw) != mp.end()) {
						flg = 1;
					}
					return;
				}
				if(fg[u]) return;
				dfs2(u << 1, nw + a[u << 1]), dfs2(u << 1 | 1, nw + a[u << 1 | 1]);
			};
			dfs(j << 1, a[j << 1]), dfs2(j << 1 | 1, a[j << 1 | 1]);
			if(flg) return j;
		}
	}
	return 0;
}

int ans, tk[20];

void dfs(int u, int sm = 0) {
	int t = find_edge();
//	Debug(u, t);
	if(!t) {
		bool flg = 1;
		int sm = 0;
		dF(j, n, 1) {
			sm += tk[j];
			flg &= (sm <= n - j + 1);
		}
		if(flg) ans = min(ans, u - 1);
		return;
	}
	fg[t << 1] = 1;
	if(sm + 1 > n - (__lg(t) + 1) + 1) {
		return;
	}
	tk[__lg(t) + 1]++;
	dfs(u + 1, sm + 1);
	fg[t << 1] = 0;
	fg[t << 1 | 1] = 1;
	dfs(u + 1, sm + 1);
	tk[__lg(t) + 1]--;
	fg[t << 1 | 1] = 0;
}

void solve() {
	n = ri();
	W = (1 << n);
	F(i, 2, W + W - 1) a[i] = ri();
	ans = inf;
	dfs(1);
	if(ans == inf) puts("-1");
	else cout << ans << '\n';
}

bool Med;
signed main() {
	// Mry;
	int T = ri();
	while(T--) {
		solve();
	}
	// Try;
	return 0;
}

/*
1
3
83 3 74 14 45 17 22 41 62 74 25 1 56 22
*/