#include <bits/stdc++.h>
#define rep(x, l, r) for(int x = l; x <= r; x++)
#define repd(x, r, l) for(int x = r; x >= l; x--)
#define clr(x, y) memset(x, y, sizeof(x))
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define SZ(x) ((int)x.size())
#define int long long
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

const int INF = 0x3f3f3f3f;
const int MAXN = 5e5 + 5;
int cnt, tot;
int head[MAXN], nxt[MAXN * 2], to[MAXN * 2], value[MAXN * 2];
int dfn[MAXN * 20], depth[MAXN * 20], pos[MAXN], sum[MAXN], f[MAXN];
int lg[MAXN], st[MAXN][35], rev[MAXN][35];

pii res[MAXN];

void init(){
    cnt = tot = 0;
    clr(head, -1);
}

void addedge(int u, int v, int w){
    nxt[cnt] = head[u];
    head[u] = cnt;
    to[cnt] = v;
    value[cnt] = w;
    cnt++;
}

void dfs(int u, int dep){
    dfn[++tot] = u;
    depth[tot] = dep;
    pos[u] = tot;
    for(int e = head[u]; e != -1; e = nxt[e]){
        int v = to[e];
        if(!pos[v]){
            sum[v] = sum[u] + value[e];
            dfs(v, dep + 1);
            dfn[++tot] = u;
            depth[tot] = dep;
        }
    }
}

int lca(int l, int r){
    int k = lg[r - l + 1];
    return st[l][k] < st[r + 1 - (1 << k)][k] ? rev[l][k] : rev[r + 1 - (1 << k)][k];
}

int query(int x, int y){
    int rt = lca(min(pos[x], pos[y]), max(pos[x], pos[y]));
    // printf("    %d %d %d\n", x, y, rt);
    return sum[x] + sum[y] - 2 * sum[rt];
}

int check(int x, int k, int mid){
    if(res[mid].fi == -1 || res[mid].se == -1) return 0;
    int ans = 0;
    if(res[mid].fi) ans = max(ans, query(x, res[mid].fi));
    if(res[mid].se) ans = max(ans, query(x, res[mid].se));
    // printf("%d %d %d : %d %d : %d\n", x, k, mid, res[mid].fi, res[mid].se, ans);
    // printf("%d %d\n", )
    return ans <= k;
}

signed main(){
    int n, q;
    scanf("%lld%lld", &n, &q);
    clr(f, -1);
    rep(i, 1, n){
        int x;
        scanf("%lld", &x);
        if(x < n) f[x] = i;
    }
    init();
    rep(i, 1, n - 1){
        int u, v, w;
        // printf("%lld\n", i);
        scanf("%lld%lld%lld", &u, &v, &w);
        addedge(u, v, w);
        addedge(v, u, w);
    }
    dfs(1, 1);
    // puts("xxxx");
    rep(i, 2, tot + 1) lg[i] = lg[i >> 1] + 1;
    rep(i, 1, tot) st[i][0] = depth[i], rev[i][0] = dfn[i];
    rep(j, 1, lg[tot]){
        rep(i, 1, tot - (1 << j) + 1){
            if(st[i][j - 1] < st[i + (1 << (j - 1))][j - 1]){
                st[i][j] = st[i][j - 1];
                rev[i][j] = rev[i][j - 1];
            }
            else{
                st[i][j] = st[i + (1 << (j - 1))][j - 1];
                rev[i][j] = rev[i + (1 << (j - 1))][j - 1];
            }
        }
    }
    res[0] = mp(f[0], 0);
    res[1] = mp(f[0], f[1]);
    rep(i, 2, n - 1){
        if(res[i - 1].fi == -1 || res[i - 1].se == -1 || f[i] == -1){
            res[i].fi = res[i].se = -1;
            continue;
        }
        int s1 = query(res[i - 1].fi, res[i - 1].se),
        s2 = query(res[i - 1].fi, f[i]),
        s3 = query(res[i - 1].se, f[i]);
        if(s1 >= s2 && s1 >= s3) res[i] = res[i - 1];
        else if(s2 >= s1 && s2 >= s3) res[i] = mp(res[i - 1].fi, f[i]);
        else res[i] = mp(res[i - 1].se, f[i]);
    }
    // rep(i, 0, 3) printf("%d : %d %d\n", i, res[i].fi, res[i].se);
    // puts("xxx");
    while(q--){
        int x, k;
        scanf("%lld%lld", &x, &k);
        int l = 0, r = n - 1, ans = -1;
        while(l <= r){
            int mid = (l + r) >> 1;
            if(check(x, k, mid)){
                ans = mid;
                l = mid + 1;
            }
            else r = mid - 1;
        }
        printf("%lld\n", ans + 1);
    }
    return 0;
}