#include<bits/stdc++.h>
#define int long long
#define inf 1e15
using namespace std;
const int maxn=1000010;
int n,q;
int a[maxn],t[maxn<<2],lazy[maxn<<2],lazy2[maxn<<2];
inline int read()
{
	int 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;
}
inline void Pushup(int k)
{
	t[k] = max(t[k<<1], t[k<<1|1]);
}
inline void Pushdown2(int k)
{
	if(lazy2[k]!=-1145141919810)
	{
		lazy[k<<1] = lazy[k<<1|1] = 0;
		lazy2[k<<1] = lazy2[k];
		lazy2[k<<1|1] = lazy2[k];
		t[k<<1] = lazy2[k];
		t[k<<1|1] = lazy2[k];
		lazy2[k] = -1145141919810;
	}
}
inline void Pushdown(int k)
{
	if(lazy[k])
	{
		Pushdown2(k);
		lazy[k<<1] += lazy[k];
		lazy[k<<1|1] += lazy[k];
		t[k<<1] += lazy[k];
		t[k<<1|1] += lazy[k];
		lazy[k] = 0;
	}
}
void build(int k,int l,int r)
{
	if(l == r)
	{
		lazy[k] = 0;
		lazy2[k] = -1145141919810;
		t[k] = a[l];
	}
	else
	{
		int m = (l+r)>>1;
		build(k<<1,l,m);
		build(k<<1|1,m+1,r);
		Pushup(k);
	}
}
inline void updata(int L,int R,int v,int l,int r,int k)
{
	if(L <= l && r <= R)
	{
		Pushdown2(k);
		t[k] += v,lazy[k] += v;
		return;
	}
	else
	{
		Pushdown2(k);
		Pushdown(k);
		int m = (l+r)>>1;
		if(L <= m)
			updata(L,R,v,l,m,k<<1);
		if(R > m)
			updata(L,R,v,m+1,r,k<<1|1);
		Pushup(k);
	}
}
inline void updata2(int L,int R,int v,int l,int r,int k)
{
	if(L <= l && r <= R)
	{
		lazy[k] = 0;
		t[k] = v,lazy2[k] = v;
		return;
	}
	else
	{
		Pushdown2(k);
		Pushdown(k);
		int m = (l+r)>>1;
		if(L <= m)
			updata2(L,R,v,l,m,k<<1);
		if(R > m)
			updata2(L,R,v,m+1,r,k<<1|1);
		Pushup(k);
	}
}
inline int query(int L,int R,int l,int r,int k)
{
	if(L <= l && r <= R)return t[k];
	else
	{
		Pushdown2(k);
		Pushdown(k);
		int res = -inf;
		int m = (l+r)>>1;
		if(L <= m)
			res = max(res, query(L,R,l,m,k<<1));
		if(R > m)
			res = max(res, query(L,R,m+1,r,k<<1|1));
		return res;
	}
}
signed main()
{
	n = read(),q = read();
	for(int i=1;i<=n;i++)
	{
		a[i] = read();
	}
	build(1,1,n);
	for(int i=1;i<=n<<2;i++)lazy2[i]=-1145141919810;
	while(q--)
	{
		int op,l,r,x;
		op = read(),l = read(),r = read();
		if(op == 1)
		{
			x = read();
			updata2(l,r,x,1,n,1);
		}
		if(op == 2)
		{
			x = read();
			updata(l,r,x,1,n,1);
		}
		if(op == 3)
		{
			printf("%lld\n",query(l,r,1,n,1));
		}
	}
	return 0;
}

题目