原本是 TLE 的，然后卡了卡常，发现还有 MLE，人麻了，求卡空间。

#include<bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5, M = 1.68e7 + 5;

inline int read(){
	int x = 0, f = 1; char c = getchar();
	while(!isdigit(c)) { if(c == '-') f = -1; c = getchar(); }
	while(isdigit(c)) { x = x * 10 + c - '0'; c = getchar(); }
	return x * f;
}

int ls[M], rs[M], xor_sum[M];
int num, n;
vector<pair<int, int> >q[N];

inline void modify(int &k, int l, int r, int x, int v){
	k = ++num; xor_sum[k] = v;
	if(l == r) { return; }
	int mid = l + r >> 1;
	if(x <= mid) modify(ls[k], l, mid, x, v);
	else modify(rs[k], mid + 1, r, x, v);
}

inline int merge(int x, int y){
	if(!x || !y) return x | y;
	ls[x] = merge(ls[x], ls[y]), rs[x] = merge(rs[x], rs[y]);
	xor_sum[x] = xor_sum[x] ^ xor_sum[y];
	return x;
}

inline int query(int k, int l, int r, int ql, int qr){
	if(l >= ql && r <= qr) return xor_sum[k];
	int mid = l + r >> 1, ans = 0;
	if(ql <= mid) ans = query(ls[k], l, mid, ql, qr);
	if(qr > mid) ans ^= query(rs[k], mid + 1, r, ql, qr);
	return ans;
}

struct edge{
	int to, next;
}e[N];
int head[N], cnt;
void add(int u, int v){
	e[cnt] = {v, head[u]};
	head[u] = cnt++;
}

void init(){
	memset(head, -1, sizeof(head));
	cnt = 0;
}
int a[N], dep[N];

inline void dfs(int u, int fa){
	dep[u] = dep[fa] + 1;
	for(register int i = head[u], v; ~i; i = e[i].next){
		v = e[i].to;
		if(v == fa) continue;
		dfs(v, u);
	}
}

int ans[N];

inline int dfs2(int u, int fa){
	int rt;
	modify(rt, 1, n, dep[u], a[u]);
	for(register int i = head[u], v; ~i; i = e[i].next){
		v = e[i].to;
		rt = merge(rt, dfs2(v, u));
	}
	for(auto [x, d] : q[u]){
		ans[x] = query(rt, 1, n, dep[u], min(n, dep[u] + d));
	}
	return rt;
}

inline void solve(){
	int m; n = read(), m = read(); init();
	for(register int i = 1; i <= n; i++) a[i] = read();
	for(register int i = 1; i < n; i++){
		int p = read();
		add(p, i + 1);
	}
	for(register int i = 1; i <= m; i++){
		int u = read(), h = read();
		q[u].push_back({i, h});
	}
	dfs(1, 0); dfs2(1, 0);
	cout << fixed << setprecision(3);
	for(register int i = 1; i <= m; i++) cout << (double)(ans[i]) / 1000.0 << '\n';
}

int main(){
	int t = 1;
	//cin >> t;
	while(t--){
		solve();
	}
	return 0;
}