#include <bits/stdc++.h>
#GCC optimize("Ofast")
#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;
}