#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int maxN = 1e5+5;
int t, n, m;
int f[maxN];

int find(int v) {
	if (f[v] == v) {
		return v;
	}
	f[v] = find(f[v]);
	return f[v];
}

void merge(int a, int b) {
	int ra = find(a);
	int rb = find(b);
	if (ra != rb) {
		f[ra] = rb;
	}
}

ll sqr (int v) {
	return (ll) v * v;
}

ll findDist(vector<int> a, vector<int> b) {
	ll ret = maxN;
	for (int i=0; i<a.size(); i++) {
		int left = 0; int right = b.size() - 1;
		int pos = -1;
		while (left <= right) {
			int mid = (left + right) / 2;
			if (b[mid] > a[i]) {
				pos = mid;
				right = mid - 1;
			} else {
				left = mid + 1;
			}
		}
		if (pos == -1) {
			ret = min(ret, sqr(a[i] - b[b.size() - 1]));
		} else if (pos == 0) {
			ret = min(ret, sqr(a[i] - b[0]));
		} else {
			ll distRight = sqr(a[i] - b[pos]);
			ll distLeft = sqr(a[i] - b[pos - 1]);
			ret = min(ret, min(distLeft, distRight));
		}
	}
	return ret;
}

void solve() {
	scanf("%d %d", &n, &m);
	for (int i=1; i<=n; i++) {
		f[i] = i;
	}
	for (int i=0; i<m; i++) {
		int a, b;
		cin >> a >> b;
		merge(a, b);
	}
	vector<int> sets[n+1];
	for (int i=1; i<=n; i++) {
		sets[find(i)].push_back(i);
	}
	int root1 = find(1);
	int rootn = find(n);
	if (root1 == rootn) {
		printf("0\n");
		return;
	}
	ll ans = findDist(sets[root1], sets[rootn]);
	for (int i=1; i<=n; i++) {
		if (i != root1 && i != rootn && sets[i].size() > 0) {
			ans = min(ans, findDist(sets[i], sets[root1]) + findDist(sets[i], sets[rootn]));
		}
	}
	printf("%d\n", ans);
}

int main() {
	scanf("%d", &t);
	for (int ti=0; ti<t; ti++) {
		solve();
	}
	return 0;
}