#include<bits/stdc++.h>
using namespace std;
const long long N=10e6+10 , MIN = LONG_LONG_MIN;
typedef long long ll;
long long n,m,a[N];
struct tree
{
	ll l,r;
	ll sum,add,s;//s操作2 add操作1
}tr[4*N];

void build(int u,int l,int r)
{
	tr[u] = {l,r,MIN,MIN,MIN};
	ll mid = l+r >> 1;
	if(l == r) tr[u].sum = a[l];
	else{
		build(u << 1,l,mid),build(u << 1|1,mid+1,r);
		tr[u].sum = max(tr[u << 1].sum , tr[u << 1|1].sum);
	}
}

void pushdown_s(int u)
{
	auto &a=tr[u],&b=tr[u << 1],&c=tr[u << 1|1];
	if(a.s!=MIN){
		b.add = c.add = MIN;
		
		b.s=a.s; b.sum = a.s;
		c.s=a.s; c.sum = a.s;
		a.s=MIN;
	}
}

void pushdown_a(int u)
{
	auto &a=tr[u],&b=tr[u << 1],&c=tr[u << 1|1];
	if(a.add!=MIN){
		b.add+=a.add; b.sum += a.add;
		c.add+=a.add; c.sum += a.add;
		a.add = MIN;
	}
}

void update_s(int u,int x,int y,int w)
{
	int l = tr[u].l , r = tr[u].r , mid = l+r >> 1;
	if(x<=l&&y>=r) {
		tr[u].sum = w;
		tr[u].s = w;
	}
    else{
		pushdown_s(u);
		pushdown_a(u);
		if(x<=mid) update_s(u << 1,x,y,w);
		if(y>mid)  update_s(u << 1|1,x,y,w);
		tr[u].sum = max(tr[u << 1].sum,tr[u << 1|1].sum);
	} 
}

void update_a(ll u,ll x,ll y,ll w)
{
	ll l = tr[u].l , r = tr[u].r , mid = l+r >> 1;
	if(x<=l&&y>=r) {
		tr[u].sum += w;
		tr[u].add += w;
	}
	else{
	    pushdown_s(u);
		pushdown_a(u);
		if(x<=mid) update_a(u << 1,x,y,w);
		if(y>mid)  update_a(u << 1|1,x,y,w);
		tr[u].sum = max(tr[u << 1].sum,tr[u << 1|1].sum);
	} 
}
ll query(ll u,ll x,ll y)
{
	ll l = tr[u].l , r = tr[u].r , mid = l+r >> 1;
	if(x<=l&&y>=r) return tr[u].sum;
	else{
		pushdown_s(u);
		pushdown_a(u);
		long long inf = LONG_LONG_MIN;
		if(x<=mid) inf = max(inf,query(u << 1,x,y));
		if(y>mid)  inf = max(inf,query(u << 1|1,x,y));
		return inf ;
	}
}

int main()
{
	cin >> n >> m;
	for(int i=1;i<=n;i++) scanf("%lld",&a[i]);
	build(1,1,n);
	while(m--){
		ll op,x,y,k;
		scanf("%lld",&op);
		if(op == 1){
			scanf("%lld%lld%lld",&x,&y,&k);
			update_s(1,x,y,k);
		}
		if(op == 2){
			scanf("%lld%lld%lld",&x,&y,&k);
			update_a(1,x,y,k);
		}
		if(op == 3){
			scanf("%lld%lld",&x,&y);
			printf("%lld\n",query(1,x,y));
		}
	}
}