#include <bits/stdc++.h>
#include <cstdio>
#define ll long long 
#define INF 0x3f3f3f3f
using namespace std;
const int N = 1e6 + 10;
inline ll read(){
	ll x = 0, f = 1;
	char ch = getchar();
	while(ch < '0' || ch > '9'){
		if(ch == '-') f = -1;
		ch = getchar();
	}
	while(ch >= '0' && ch <= '9'){
		x = x * 10 + ch - '0';
		ch = getchar();
	}
	return x * f;
}
struct node{
	ll l, r; // l左子树 r右子树
	ll add, pt; // add添加标记 pt替换标记
	ll maxn;// 最大值
}tr[N * 4];
int n, m;
ll a[N];
inline void pushup(int p){ // 找最大值
	tr[p].maxn = max(tr[p * 2].maxn, tr[p * 2 + 1].maxn);
}
inline void build(ll l, ll r, ll p){//建树
	tr[p].l = l;
	tr[p].r = r;
	tr[p].pt = INF;
	tr[p].add = 0;
	if(l == r){
	tr[p].maxn = a[l];
	return ;
	}	
	ll mid = (l + r) / 2;
	build(l, mid, p * 2);
	build(mid + 1, r, p * 2 + 1);
	pushup(p);
}
inline void pushdown(int p){ // 下穿懒标记
	if(tr[p].pt != INF){ // 判断替换标记
		tr[p * 2].pt = tr[p * 2 + 1].pt = tr[p].pt;
		tr[p * 2].maxn = tr[p * 2 + 1].maxn = tr[p].pt;
		tr[p * 2].add = tr[p * 2 + 1].add = tr[p].add = 0 ;
		tr[p].pt = INF;
	}
	if(tr[p].add){	// 判断添加标记
		tr[p * 2].add += tr[p].add;
		tr[p * 2 + 1].add += tr[p].add;
		tr[p * 2 + 1].maxn += tr[p].add;
		tr[p * 2].maxn += tr[p].add;
		tr[p].add = 0;
	}
}
inline void op1(ll l, ll r, ll c, ll p){ //替换操作
	if(l <= tr[p].l && r >= tr[p].r){
		tr[p].add = 0;
		tr[p].pt = c;
		tr[p].maxn = c;
		return ;
	}
	pushdown(p);
	ll mid = (tr[p].l + tr[p].r) / 2;
	if(l <= mid) op1(l, r, c, p * 2);
	if(r > m) op1(l, r, c, p * 2 + 1);
	pushup(p);
}
inline void op2(ll l, ll r, ll c, ll p){ // 添加操作
	if(l <= tr[p].l && r >= tr[p].r){
		tr[p].maxn += c;
		tr[p].add += c;
		return ;
	}
	pushdown(p);
	ll mid = (tr[p].l + tr[p].r) / 2;
	if(l <= mid) op2(l, r, c, p * 2);
	if(r > mid)op2(l, r, c, p * 2 + 1);
	pushup(p);
}
inline ll op3(ll l, ll r, ll p){ // 求和操作
	if(l <= tr[p].l && r >= tr[p].r){
		return tr[p].maxn;
	}
	pushdown(p);
	ll mid = (tr[p].l + tr[p].r) / 2;
	ll sum = -1e12;
	if(l <= mid)sum = 1LL*max(1LL*sum, 1LL*op3(l, r, p * 2));
	if(r > mid)sum = 1LL*max(1LL*sum, 1LL*op3(l, r, p * 2 + 1));
	return sum;
}
signed main(){
	n = read(), m = read();
	for(int i = 1; i <= n; i ++ )a[i] = read();
	int op, x1, x2, x3;
	build(1, n, 1);
	for(int i = 1; i <= m; i ++ ){
		op = read(), x1 = read(), x2 = read();
		if(op == 1){
			x3 = read();
		op1(x1, x2, x3, 1);
		}
		if(op == 2){
			x3 = read();
		op2(x1, x2, x3, 1);
		}
		if(op == 3){
		printf("%lld\n", 1LL*op3(x1, x2, 1));
		}
	}
	return 0;
}