#include <bits/stdc++.h>
#define _rep(i, x, y) for(int i = x; i <= y; ++i)
#define _req(i, x, y) for(int i = x; i >= y; --i)
#define _rev(i, u) for(int i = head[u]; i; i = e[i].nxt)
#define pb push_back
#define fi first
#define se second
#define mst(f, i) memset(f, i, sizeof f)
using namespace std;
#ifdef ONLINE_JUDGE
#define debug(...) 0
#else
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#endif
typedef long long ll;
typedef pair<ll, ll> PII;
namespace fastio{
    char ibuf[1 << 20],*p1 = ibuf, *p2 = ibuf;
    #define get() p1 == p2 && (p2 = (p1 = ibuf) + fread(ibuf, 1, 1 << 20, stdin), p1 == p2) ? EOF : *p1++
    template<typename T> inline void read(T &t){
        T x = 0, f = 1;
        char c = get();
        while(!isdigit(c)){
            if(c == '-') f = -f;
            c = get();
        }
        while(isdigit(c)) x = x * 10 + c - '0', c = get();
        t = x * f;
    }
    template<typename T, typename ... Args> inline void read(T &t, Args&... args){
        read(t);
        read(args...);
    }
    template<typename T> void write(T t){
        if(t < 0) putchar('-'), t = -t;
        if(t >= 10) write(t / 10);
        putchar(t % 10 + '0');
    }
    template<typename T, typename ... Args> void write(T t, Args... args){
        write(t), putchar(' '), write(args...);
    }
    template<typename T> void writeln(T t){
        write(t);
        puts("");
    }
    template<typename T> void writes(T t){
        write(t), putchar(' ');
    }
    #undef get
};
using namespace fastio;
#define multitest() int T; read(T); _rep(tCase, 1, T)
namespace Calculation{
    const ll mod = 998244353;
    ll ksm(ll p, ll h){ll base = p % mod, res = 1; while(h){if(h & 1ll) res = res * base % mod; base = base * base % mod, h >>= 1ll;} return res;}
    void dec(ll &x, ll y){x = ((x - y) % mod + mod) % mod;}
    void add(ll &x, ll y){x = (x + y) % mod;}
    void mul(ll &x, ll y){x = x * y % mod;}
    ll sub(ll x, ll y){return ((x - y) % mod + mod) % mod;}
    ll pls(ll x, ll y){return ((x + y) % mod + mod) % mod;}
    ll mult(ll x, ll y){return x * y % mod;}
}
using namespace Calculation;
const int N = 5e5 + 5, inf = 0x3f3f3f3f;
ll n, q, lst, a[N];
int ans[N];
vector<PII> G[N], h[N];
namespace sgt{
    int tr[N << 2];
    #define ls x << 1
    #define rs x << 1 | 1
    void modify(int x, int l, int r, int p, int val){
        if(l == r) return tr[x] = val, void();
        int mid = l + r >> 1;
        if(p <= mid) modify(ls, l, mid, p, val);
        else modify(rs, mid + 1, r, p, val);
        tr[x] = min(tr[ls], tr[rs]);
    }
    int query(int x, int l, int r, int L, int R){
        if(l >= L && r <= R) return tr[x];
        int mid = l + r >> 1, res = inf;
        if(L <= mid) res = min(res, query(ls, l, mid, L, R));
        if(R > mid) res = min(res, query(rs, mid + 1, r, L, R));
        return res;
    }
    void clr(int x, int l, int r){
        tr[x] = 0;
        if(l == r) return;
        int mid = l + r >> 1;
        clr(ls, l, mid), clr(rs, mid + 1, r);
    }
}
int rt, tot, maxn[N], siz[N];
bool vis[N];
void findrt(int u, int fa){
    siz[u] = 1, maxn[u] = 0;
    for(auto &[v, w] : G[u]){
        if(v == fa || vis[v]) continue;
        findrt(v, u), siz[u] += siz[v], maxn[u] = max(maxn[u], siz[v]);
    }
    maxn[u] = max(maxn[u], tot - siz[u]);
    if(maxn[u] < maxn[rt]) rt = u;
}
int cnt;
ll len, lsh[N], pos[N], nxt[N];
struct node{
    ll d, u, col;
}b[N];
void dfs(int u, int fa, ll cur, int col){
    b[++cnt] = {cur, u, col}, lsh[++len] = cur;
    for(auto &[v, w] : G[u]) if(!vis[v] && v != fa) dfs(v, u, cur + w, col);
}

void solve(int u){
    int sum = tot, lst = siz[u];
    vis[u] = 1, siz[u] = tot;
    b[++cnt] = {0, u, u}, lsh[++len] = 0;
    for(auto &[v, w] : G[u]) if(!vis[v]) dfs(v, u, w, v);
    sort(lsh + 1, lsh + 1 + len);
    _rep(i, 1, cnt){
        pos[i] = lower_bound(lsh + 1, lsh + 1 + len, b[i].d) - lsh;
        pos[i] += nxt[pos[i]]++;
        assert(pos[i] <= len);
        sgt::modify(1, 1, len, pos[i], a[b[i].u]);
    }
    _rep(i, 1, cnt){
        int j = i; sgt::modify(1, 1, len, pos[i], inf);
        while(j < cnt && b[j + 1].col == b[i].col) j++, sgt::modify(1, 1, len, pos[j], inf);
        _rep(p, i, j){
            for(auto &[k, id] : h[b[p].u]){
                int t = lower_bound(lsh + 1, lsh + 1 + len, k - b[p].d + 1) - lsh;
                if(t <= len) ans[id] = min(ans[id], sgt::query(1, 1, len, t, len));
            }
        }
        _rep(p, i, j) sgt::modify(1, 1, len, pos[p], a[b[p].u]);
        i = j;
    }
    _rep(i, 1, len) nxt[i] = 0;
    sgt::clr(1, 1, len), cnt = len = 0;
    for(auto &[v, w] : G[u]){
        if(vis[v]) continue;
        tot = (siz[v] > lst) ? sum - lst : siz[v];
        maxn[rt = 0] = 2e9, findrt(v, u);
        solve(rt);
    }
}
int main(){
    read(n, q);
    vector<int> v;
    _rep(i, 1, n) read(a[i]), v.pb(a[i]);
    sort(v.begin(), v.end());
    lst = n; _rep(i, 0, n - 1) if(v[i] != i){lst = i; break;}
    _rep(i, 2, n){
        ll u, v, w; read(u, v, w);
        G[u].pb({v, w}), G[v].pb({u, w});
    }    
    _rep(i, 1, q){
        ll x, k; read(x, k);
        h[x].pb({k, i}), ans[i] = lst;
    }
    tot = n, maxn[rt = 0] = 2e9, findrt(1, 0), solve(rt);
    _rep(i, 1, q) writeln(ans[i]);
    return 0;
}