#include<bits/stdc++.h>

using namespace std;
const int N = 210000;
const int L;
int n, q, arr[N], l[N], cnt, v[N];
vector<pair<int,int> > g[N];
int blk[N], sum[N], ans[N], num[N];
void dfs(int x, int fa) {
	l[x] = ++cnt, arr[cnt] = x;
	for (auto p: g[x]) {
		int y = p.first, w = p.second;
		if (y == fa) continue;
		v[y] = w;
		dfs(y, x);
	}
	arr[++cnt] = x;
}
struct query {
	int l, r, id;
	friend bool operator < (query a, query b) {
		if (a.l / L != b.l / L) return a.l / L < b.l / L;
		if ((a.l / L) & 1) return a.r > b.r;
		else return a.r < b.r;
	}
}a[N];
void dec(int x) {
	x = arr[x];
	int w = v[x];
	if (v[x] > n) return;
	num[x]++;
	if (num[x] % 2 == 0) {
		blk[w]--;
		if (blk[w] == 0) sum[w / L]--;
	}
	else {
		blk[w]++;
		if (blk[w] == 1) sum[w / L]++;
	}
}
int main() {
	cin >> n >> q;
	L=sqrt(n);
	for(int i=1;i<n;i++) {
		int x, y, w;
		cin >> x >> y >> w;
		g[x].push_back({y,w});
		g[y].push_back({x,w});
	}
	v[1] = n+1;
	dfs(1, 0);
	for(int i=1;i<=q;i++) {
		int x, y;
		cin >> x >> y;
		if (l[x] > l[y]) swap(x, y);
		a[i] = {l[x], l[y], i};
	}
	sort(a + 1, a + q + 1);
	int l = 1, r = 1;
	for(int i=1;i<=q;i++) {
		while (r < a[i].r) dec(++r);
		while (l > a[i].l) dec(l--);
		while (r > a[i].r) dec(r--);
		while (l < a[i].l) dec(++l);
		for (int j = 0; ; j++) 
			if (sum[j] != L) 
			{
				
				int cur = j * L;
				while (blk[cur]) cur++;
				ans[a[i].id] = cur;
				break;
			}
	}
	for(int i=1;i<=q;i++) 
		cout << ans[i] << "\n";
	return 0;
}

answer.code:5:11: error: uninitialized ‘const L’ [-fpermissive]
    5 | const int L;
      |           ^
answer.code: In function ‘int main()’:
answer.code:43:10: error: assignment of read-only variable ‘L’
   43 |         L=sqrt(n);
      |         ~^~~~~~~~