#include<bits/stdc++.h>

#define int long long
#define F(i, j, k) for (int i = j; i <= k; i ++)
#define DF(i, j, k) for (int i = j; i >= k; i --)

using namespace std;

inline int read()
{
	int x=0,f=1;
	char c=getchar();
	while(c<'0' || c>'9')
	{
		if(c=='-') f=-1;
		c=getchar();
	}
	while(c>='0' && c<='9')
	{
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}

inline long long readlong() {
	long long x=0,f=1;
	char c=getchar();
	while(c<'0' || c>'9')
	{
		if(c=='-') f=-1;
		c=getchar();
	}
	while(c>='0' && c<='9')
	{
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}

const int N = 5e5 + 100;

struct wzy {
	int val, num;
} a[N];

inline bool cmp(wzy x, wzy y) {
	return x.val < y.val;
}

int cnt, head[N], nxt[N << 1], to[N << 1], val[N << 1];

inline void addedge(int x, int y, int w) {
	nxt[++cnt] = head[x];
	to[cnt] = y;
	val[cnt] = w;
	head[x] = cnt;
}

int n, fa[N][21], depth[N], lg[N];

long long di[N];

inline void dfs(int x) {
	for (int i = head[x]; i; i = nxt[i]) {
		if (to[i] == fa[x][0]) continue;
		fa[to[i]][0] = x;
		depth[to[i]] = depth[x] + 1;
		di[to[i]] = di[x] + val[i];
		dfs(to[i]);
	}
}

inline void prepare() {
	depth[1] = 1;
	dfs(1);
	F(i, 1, 20)
		F(j, 1, n)
			fa[j][i] = fa[fa[j][i - 1]][i - 1];
	lg[1] = 0;
	F(i, 2, n) lg[i] = lg[i >> 1] + 1;
}

inline int lca(int x, int y) {
	if (depth[y] > depth[x]) swap(x, y);
	DF(i, lg[depth[x] - depth[y]], 0)
		if (depth[fa[x][i]] >= depth[y]) x = fa[x][i];
	if (x == y) return x;
	DF(i, lg[depth[x]], 0)
		if (fa[x][i] != fa[y][i]) { x = fa[x][i]; y = fa[y][i]; }
	return fa[x][0];
}

inline long long dis(int x, int y) {
	return di[x] + di[y] - 2LL * di[lca(x, y)];
}

int X[N], Y[N];

signed main()
{
	n = read();
	int Q = read();

	F(i, 1, n) {
		a[i].val = read();
		a[i].num = i;
	}
	sort(a + 1, a + n + 1, cmp);
	int ans = n, mx = n;
	F(i, 1, n)
		if (a[i].val != i - 1) {
			ans = i - 1;
			mx = i - 1;
			break;
		}
	F(i, 1, n - 1) {
		int x = read(), y = read(), w = read();
		addedge(x, y, w);
		addedge(y, x, w);
	}
	prepare();
	long long cur = 0;
	F(i, 1, mx) {
		if (i == 1) { X[i] = Y[i] = a[i].num; continue; }
		X[i] = X[i - 1];
		Y[i] = Y[i - 1];
		long long dis1 = dis(a[i].num, X[i - 1]), dis2 = dis(a[i].num, Y[i - 1]);
		if (dis1 > cur) {
			cur = dis1;
			X[i] = X[i - 1];
			Y[i] = a[i].num;
		}
		if (dis2 > cur) {
			cur = dis2;
			X[i] = a[i].num;
			Y[i] = Y[i - 1];
		}
	}
	while (Q --) {
		int x = read();
		long long k = readlong();
		int l = 1, r = mx, an = ans;
		while (l <= r) {
			int mid = (l + r) >> 1;
			//cout << Q << ": " << mid << ' ' << x << ' ' << X[mid] << ' ' << Y[mid] << ' ' << lca(x, X[mid]) << endl;
			if (dis(x, X[mid]) <= k && dis(x, Y[mid]) <= k) l = mid + 1;
			else { an = mid - 1; r = mid - 1; }
		}
		cout << an << '\n';
	}
 	return 0;
}
/*
5 4
3 9 0 1 2
1 2 10
3 1 4
3 4 3
3 5 2
3 0
1 0
4 6
4 7

*/