#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
const int N = 2e5 + 5, inf = 2e9;
int n, q;
int h[N], rt1[N], rt2[N];
struct tree1{
#define mid ((l + r) >> 1)
	int tot;
	struct node{
		int ls, rs, mx;
	}a[N * 20];
	void build(int &p, int l, int r){
		p = ++tot;
		if (l == r){
			a[p].mx = h[l];
			return;
		}
		build(a[p].ls, l, mid);
		build(a[p].rs, mid + 1, r);
		a[p].mx = max(a[a[p].ls].mx, a[a[p].rs].mx);
	}
	void add(int &p, int l, int r, int s, int k){
		a[++tot] = a[p];
		p = tot;
		if (l == r) return a[p].mx = k, void();
		if (s <= mid) add(a[p].ls, l, mid, s, k);
		else add(a[p].rs, mid + 1, r, s, k);
		a[p].mx = max(a[a[p].ls].mx, a[a[p].rs].mx);
	}
	int ask(int p, int l, int r, int s, int t){
		if (s <= l && r <= t) return a[p].mx;
		int res = 0;
		if (s <= mid) res = max(ask(a[p].ls, l, mid, s, t), res);
		if (t > mid) res = max(ask(a[p].rs, mid + 1, r, s, t), res);
		return res;
	}
	int ask1(int p, int l, int r, int s, int k){
		if (r <= s){
			if (a[p].mx < k) return 0;
			else if (l == r) return l;
			else if (a[a[p].rs].mx >= k) return ask1(a[p].rs, mid + 1, r, s, k);
			else return ask1(a[p].ls, l, mid, s, k);
		}
		int res = 0;
		if (mid < s) res = ask1(a[p].rs, mid + 1, r, s, k);
		if (res) return res;
		else return ask1(a[p].ls, l, mid, s, k);
	}
	int ask2(int p, int l, int r, int s, int k){
		if (s <= l){
			if (a[p].mx < k) return n;
			else if (l == r) return r;
			else if (a[a[p].ls].mx >= k) return ask2(a[p].ls, l, mid, s, k);
			else return ask2(a[p].rs, mid + 1, r, s, k);
		}
		int res = n;
		if (s <= mid) res = ask2(a[p].ls, l, mid, s, k);
		if (res < n) return res;
		else return ask2(a[p].rs, mid + 1, r, s, k);
	}
}T1;
struct tree2{
	int tot;
	struct node{
		int ls, rs;
		int t, tag;//t = t >> 2, type = t & 3
	}a[N * 36];
	void add(int &p, int l, int r, int s, int t, int _t, int _tag){
		a[++tot] = a[p];
		p = tot;
		if (s <= l && r <= t){
			a[p].t = _t, a[p].tag = _tag;
			return;
		}
		if (s <= mid) add(a[p].ls, l, mid, s, t, _t, _tag);
		if (t > mid) add(a[p].rs, mid + 1, r, s, t, _t, _tag);
	}
	pair<int, int> ask(int p, int l, int r, int s){
		pair<int, int> res(a[p].t, a[p].tag);
		if (l == r) return res;
		if (s <= mid) res = max(ask(a[p].ls, l, mid, s), res);
		else res = max(ask(a[p].rs, mid + 1, r, s), res);
		return res;
	}
#undef mid
}T2;
int aska(int i, int x){
	pair<int, int> res = T2.ask(rt2[i], 0, n, x);
	int t = res.first, p = res.second;
	if (!t) return 0;
	else if ((t & 3) == 1) return p;
	else if (x == p) return 0;
	else if (x < p) return T1.ask(rt1[t >> 2], 0, n, x, p - 1);
	else return T1.ask(rt1[t >> 2], 0, n, p, x - 1);
}
int main(){
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
//	freopen("in.txt", "r", stdin);
//	freopen("out.txt", "w", stdout);
	cin >> n >> q;
	h[0] = h[n] = inf;
	for (int i = 1; i < n; i++)
		cin >> h[i];
	T1.build(rt1[0], 0, n);
	for (int i = 1; i <= q; i++){
		int opt, t, x;
		cin >> opt >> t >> x;
		rt1[i] = rt1[t], rt2[i] = rt2[t];
		if (opt == 0){
			int y;
			cin >> y;
			if (aska(i, x) < y){
				int l = T1.ask1(rt1[i], 0, n, x - 1, y), r = T1.ask2(rt1[i], 0, n, x, y);
				T2.add(rt2[i], 0, n, l + 1, r, (i << 2) | 1, y);
			}
		}else if (opt == 1){
			int y = aska(i, x);
			int l = T1.ask1(rt1[i], 0, n, x - 1, y), r = T1.ask2(rt1[i], 0, n, x, y);
			T2.add(rt2[i], 0, n, l + 1, r, (i << 2) | 2, x);
		}else if (opt == 2){
			cin >> h[x];
			T1.add(rt1[i], 0, n, x, h[x]);
		}else cout << aska(i, x) << endl;
	}
	return 0;
}