rt

#include <iostream>
#include <cstdio>
#include <cctype>
#define ll long long
#define in l <= s && r >= t
#define ot l > t || r < s
#define getmid ll mid = s - ((t - s) >> 1);

using namespace std;
const int N = 1e6+5;
ll n, q, a[N];
ll tot, root;

struct node{
    ll cto, add;//change_to, add
    ll _max;
    bool changed;
}d[N<<1];
ll ls[N<<1], rs[N<<1];

inline ll read(){
    ll x = 0, w = 1;
    char ch = getchar();
    while(!isdigit(ch)){
        if(ch == '-')w = -1;
        ch = getchar();
    }
    while(isdigit(ch)){
        x = x * 10 + (ch - '0');
        ch = getchar();
    }
    return x * w;
}

inline void pushup(ll& p){
    d[p]._max = max(d[ls[p]]._max, d[rs[p]]._max);
}
inline void pushdown(ll s, ll t, ll& p){
    if(d[p].changed){
        d[ls[p]].cto = d[p].cto;
        d[rs[p]].cto = d[p].cto;
        d[ls[p]].add = d[p].add;
        d[rs[p]].add = d[p].add;
        d[ls[p]]._max = d[p].cto + d[p].add;
        d[rs[p]]._max = d[p].cto + d[p].add;
        d[ls[p]].changed = d[rs[p]].changed = 1;
    }
    else {
        d[ls[p]].add += d[p].add;
        d[rs[p]].add += d[p].add;
        d[ls[p]]._max += d[p].add;
        d[rs[p]]._max += d[p].add;
    }
    d[p].add = d[p].cto = d[p].changed = 0;
}
inline void build(ll s, ll t, ll& p){
    if(!p)p = ++tot;
    d[p]._max = -1e18;
    if(s == t){
        d[p]._max = a[s];
        return ;
    }
    getmid
    build(s, mid, ls[p]);
    build(mid+1, t, rs[p]);
    pushup(p);
}
inline void change(ll l, ll r, ll k, ll s, ll t, ll& p){
    if(ot)return ;
    if(in){
        d[p].add = 0;
        d[p]._max = k;
        d[p].changed = 1;
        d[p].cto = k;
        return ;
    }
    pushdown(s, t, p);
    getmid
    change(l, r, k, s, mid, ls[p]);
    change(l, r, k, mid+1, t, rs[p]);
    pushup(p);
}
inline void update(ll l, ll r, ll k, ll s, ll t, ll& p){
    if(ot)return ;
    if(in){
        d[p].add += k;
        d[p]._max += k;
        return ;
    }
    pushdown(s, t, p);
    getmid
    update(l, r, k, s, mid, ls[p]);
    update(l, r, k, mid+1, t, rs[p]);
    pushup(p);
}
inline ll getmax(ll l, ll r, ll s, ll t, ll& p){
    if(ot)return -1e18;
    if(in){
        return d[p]._max;
    }
    pushdown(s, t, p);
    getmid
    ll res = -1e18;
    res = max(res, getmax(l, r, s, mid, ls[p]));
    res = max(res, getmax(l, r, mid+1, t, rs[p]));
    return res;
}

int main(){

    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    //freopen("1253.in", "r", stdin);
    //freopen("1253.out", "w", stdout);

    n = read(), q = read();
    for(int i = 1; i <= n; i++){
        a[i] = read();
    }
    build(1ll, n, root);

    for(int i = 1; i <= q; i++){
        ll opt = read(), x = read(), y = read();
        if(opt == 1){
            ll k = read();
            change(x, y, k, 1ll, n, root);//修改
        }
        else if(opt == 2){
            ll k = read();
            update(x, y, k, 1ll, n, root);//加
        }
        else {
            ll res = getmax(x, y, 1ll, n, root);//求区间最大值
            cout << res << endl;
        }
    }

    return 0;
}