#include <vector>
#include <set>
#include <iostream>

using namespace std;
using ll = int;
const ll inf = 1e9-5;
struct X {
	set<ll> vals;
};

ll closest(ll x, set<ll> &a) {
	auto u = a.upper_bound(x);
	auto l = a.lower_bound(x);
	ll ans = -inf;
	if (u != a.begin()) 
		ans = *prev(u);
	if (l != a.end()) 
		if (abs(ans-x) > abs(*l-x)) ans = *l;
	return ans;
}

ll closest(ll x, ll y, ll z) {
	if (abs(x-y) < abs(x-z)) return y;
	else return z;
}

struct Segtree {
	ll n;
	vector<set<int>> tree;
	Segtree(ll n): n(n), tree(2*n) {
	}

	void insert(ll idx, ll val) {
		idx += n;
		while (idx > 0) {
			tree[idx].insert(val);
			idx /= 2;
		}
	}

	ll act(ll l, ll r, ll targ) {
		int out = -inf;
		for (l+=n,r+=n; l < r; l /= 2, r /= 2) {
			if ((l&1)) {
				out = closest(targ, out, closest(targ, tree[l]));
				l++;
			}
			if (r&1) {
				r--;
				out = closest(targ, out, closest(targ, tree[r]));
			}
		}
		return out;
	}
};

void solve() {
	int n, m; cin >> n >> m;
	Segtree s(n);
	for (int i = 0; i < m; i++) {
		ll type; cin >> type;
		if (type == 0) {
			ll x, h; cin >> x>> h;
			s.insert(x-1, h);
		}
		else {
			ll l, r, h; cin >> l >> r >> h;
			l--;
			ll ans = s.act(l, r, h);
			if (ans == -inf) cout << -1 << endl;
			else cout << abs(ans-h) << endl;
		}
	}

}

int main() {
	int t; cin >> t;
	while (t--) solve();

}