#include <climits>
#include <iostream>
#include <vector>
using namespace std;
vector<long long> lazy1;
vector<long long> lazy2;
vector<long long> tree;
vector<long long> a;
long long n;
void build(long long p = 1, long long l = 1, long long r = n){
    if (l == r){
        tree[p] = a[l];
        return;
    }
    long long mid = (l + r) >> 1;
    build(p * 2, l, mid);
    build(p * 2 + 1, mid + 1, r);
    tree[p] = max(tree[p * 2], tree[p * 2 + 1]);
}
void push_down(long long p, long long l, long long r){
    if (lazy1[p] != LLONG_MIN){
        if (l != r){
            lazy1[p * 2] = lazy1[p];
            lazy2[p * 2] = 0;
            lazy1[p * 2 + 1] = lazy1[p];
            lazy2[p * 2 + 1] = 0;
            tree[p * 2] = lazy1[p];
            tree[p * 2 + 1] = lazy1[p];
        }
        lazy1[p] = LLONG_MIN;
        lazy2[p] = 0;
    }
    if (lazy2[p] != 0){
        if (l != r){
            lazy2[p * 2] += lazy2[p];
            lazy2[p * 2 + 1] += lazy2[p];
            tree[p * 2] += lazy2[p];
            tree[p * 2 + 1] += lazy2[p];
        }
        lazy2[p] = 0;
    }
}
void change1(long long x, long long y, long long z, long long p = 1, long long l = 1, long long r = n){
    if (r < x || l > y){
        return;
    }
    push_down(p, l, r);
    if (l >= x && r <= y){
        tree[p] = z;
        lazy1[p] = z;
        return;
    }
    long long mid = (l + r) >> 1;
    change1(x, y, z, p * 2, l, mid);
    change1(x, y, z, p * 2 + 1, mid + 1, r);
    tree[p] = max(tree[p * 2], tree[p * 2 + 1]);
}
void change2(long long x, long long y, long long z, long long p = 1, long long l = 1, long long r = n){
    if (r < x || l > y){
        return;
    }
    push_down(p, l, r);
    if (l >= x && r <= y){
        tree[p] += z;
        lazy2[p] += z;
        return;
    }
    long long mid = (l + r) >> 1;
    change2(x, y, z, p * 2, l, mid);
    change2(x, y, z, p * 2 + 1, mid + 1, r);
    tree[p] = max(tree[p * 2], tree[p * 2 + 1]);
}
long long find(long long x, long long y, long long p = 1, long long l = 1, long long r = n){
    if (r < x || l > y){
        return LLONG_MIN;
    }
    push_down(p, l, r);
    if (l >= x && r <= y){
        return tree[p];
    }
    long long mid = (l + r) >> 1;
    return max(find(x, y, p * 2, l, mid), find(x, y, p * 2 + 1, mid + 1, r));
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    long long q;
    cin >> n >> q;
    a.resize(n + 1);
    for (long long i = 1; i <= n; i++){
        cin >> a[i];
    }
    tree.resize(8 * n);
    lazy1.resize(8 * n, LLONG_MIN);
    lazy2.resize(8 * n);
    build();
    while (q--){
        long long op;
        cin >> op;
        if (op == 1){
            long long l, r, x;
            cin >> l >> r >> x;
            change1(l, r, x);
        }
        if (op == 2){
            long long l, r, x;
            cin >> l >> r >> x;
            change2(l, r, x);
        }
        if (op == 3){
            long long l, r;
            cin >> l >> r;
            cout << find(l, r) << endl;
        }
    }
    return 0;
}