第二个点怎么也过不了……

#include <bits/stdc++.h>
#define int long long
#define maxn 1000005
using namespace std;
struct node{
	int lc, rc, dat;
}t[43*maxn/2];
int root[43 *maxn/2], tot;
int n, m, a[maxn], cnt;
inline int read(){
    int f=1,x=0;char ch;
    do{ch=getchar();if(ch=='-')f=-1;}while(ch<'0'||ch>'9');
    do{x=x*10+ch-'0';ch=getchar();}while(ch>='0'&&ch<='9');
    return f*x;
}
int build(int l, int r){
	int p = ++tot;
	if(l == r){
		t[p].dat = a[l];
		return p;
	}
	int mid = l + r >> 1;
	t[p].lc = build(l, mid);
	t[p].rc = build(mid + 1, r);
	t[p].dat = max(t[t[p].lc].dat , t[t[p].rc].dat);
	return p;
}
int change(int now, int l, int r, int x, int val){
	int p = ++tot;
	t[p] = t[now];
	if(l == r){
		t[p].dat = val;
		return p;
	}
	int mid = l + r >> 1;
	if(x <= mid) t[p].lc = change(t[now].lc, l, mid, x, val);
	else t[p].rc = change(t[now].rc, mid+1, r, x, val);
	t[p].dat = max(t[t[p].lc].dat , t[t[p].rc].dat);
	return p;
}
int query(int p, int l, int r, int x){
	if (l == r) return t[p].dat;
	int mid = (l + r) >> 1;
	if (x <= mid) return query(t[p].lc, l, mid, x);
	else return query(t[p].rc, mid + 1, r, x);
}
signed main(){
	n = read(), m = read();
	for(int i = 1; i <= n; i++) a[i] = read();
	root[0] = build(1, n);
	for(int i = 1, now, opt, x, val; i <= m; i++){
		now = read(), opt = read();
		if(opt == 1){
			x = read(), val = read();
			root[i] = change(root[now], 1, n, x, val);
		}
		if(opt == 2){
			x = read();
			cout << query(root[now], 1, n, x) <<endl;
			root[i] = root[now];
		}
	}
}