#include<bits/stdc++.h>
using namespace std;
#define  ll long long
#define INF 1e11;
int n, q;
const int maxn = 1e6 + 5;
ll a[maxn], val[maxn << 2], add[maxn << 2],  re[maxn << 2];
bool flag[maxn << 2];//标记是否要修改 

inline int read() {
	int ans=0,op=1;
	char c = getchar();
	while(c<'0'|| c>'9') {
		if (c == '-'){
			op = -1;
		}
		c=getchar();
	}
	while(c>='0'&& c<='9'){
		ans = ans * 10 + c - '0';
		c=getchar();
	}
	return ans * op;
}

void pushdown(int rt){
	if (flag[rt] ){
		flag[rt<<1] = true;	//修改标记 
		flag[rt<<1|1] = true;
		
		add[rt<<1] = 0;//修改加法-子节点清空 
		add[rt<<1|1] = 0;
		
		re[rt<<1] = re[rt];//修改覆盖 
		re[rt<<1|1] = re[rt];
		
		val[rt<<1] = re[rt];//修改最大值 
		val[rt<<1|1] = re[rt];
		
		flag[rt] = false;
	}	
	if (add[rt]) {
		add[rt<<1] += add[rt];
		add[rt<<1|1] += add[rt];
		val[rt<<1] += add[rt];
		val[rt<<1|1] += add[rt];
		add[rt] = 0;
		
	}
}


void pushup(int rt){
	val[rt] == max (val[rt << 1] ,val[rt << 1 | 1] );
}

void build (int rt, int l, int r){
	flag[rt] = false;
	add[rt] = 0;
	if (l == r) {
		val[rt] = a[l];
		return ;
	}
	int mid = (l + r) >> 1;
	build(rt << 1, l, mid);
	build(rt << 1 | 1, mid + 1, r);
	pushup(rt);
}

void rev(int rt, int l, int r, int ql, int qr, ll k){
	if (qr < l || ql > r){
		return ;
	}
	if (ql <= l && r <= qr){
		re[rt] = k;
		add[rt] = 0;
		val[rt] = k;
		flag[rt] = true;
		return ;
	}
	pushdown(rt);
	int mid = (l + r)>>1;
	rev(rt<<1,l,mid,ql,qr,k);
	rev(rt<<1|1,mid+1,r,ql,qr,k);
	pushup(rt);
}


void update(int rt, int l, int r, int ql, int qr, ll k){
	if (qr < l || ql > r){
		return ;
	}
	if (ql <= l && r <= qr){
		add[rt] += k;
		val[rt] += k;
		return ;
	}
	pushdown(rt);
	int mid = (l + r)>>1;
	update(rt<<1,l,mid,ql,qr,k);
	update(rt<<1|1,mid+1,r,ql,qr,k);
	pushup(rt);
}




ll ask(int rt, int l, int r, int ql, int qr){
	if (qr<l||ql>r){
		return 0;
	}
	if(ql<=l&&r<=qr){
		return val[rt];
	}
	pushdown(rt);
	int mid = (l+r)>>1;
	ll res = -INF;
	res = max(res,ask(rt<<1,l,mid,ql,qr));
	res = max(res,ask(rt<<1|1,mid+1,r,ql,qr));
	return res;
}


int main () {
	n=read(), q=read();
	for (int i = 1; i <= n; i++){
		 a[i] = read();
	}
	build(1,1,n);
	while (q--){
		int op ;
		op=read();
		if(op == 1){
			int l, r;
			ll x;
			l=read();
			r=read();
			x=read();
			rev(1,1,n,l,r,x);//修改 
		}else if(op==2){
			int l, r;
			ll x;
			l=read();
			r=read();
			x=read();
			update(1,1,n,l,r,x);
		}else {
			int l, r;
			l=read();
			r=read();
			cout << ask(1,1,n,l,r)<<'\n';
		}
	}
	return 0;
}