#include <bits/stdc++.h>
#define lc (u << 1)
#define rc (u << 1 | 1)
using namespace std;
typedef long long ll;
const int N = 1e6 + 10;
ll n, q, a[N];
struct tree {
    int l, r;
    ll sum, add, ch;
    bool vis;
}tr[N << 2];
void pushup(int u) {
    tr[u].sum = max(tr[lc].sum, tr[rc].sum);
}
void build(int u, int l, int r) {
    tr[u] = {l, r, a[l], 0, 0, 0};
    if (l == r) return;
    int mid = (l + r) >> 1;
    build(lc, l, mid);
    build(rc, mid + 1, r);
    pushup(u);
}
void pushdown(int u) {
    if (tr[u].vis) {
        tr[lc].sum = tr[u].ch;
        tr[rc].sum = tr[u].ch;
        tr[lc].vis = tr[rc].vis = true;
        tr[lc].ch = tr[rc].ch = tr[u].ch;
        tr[lc].add = tr[rc].add = 0;
        tr[u].vis = false;
    }
    tr[lc].sum += tr[u].add;
    tr[rc].sum += tr[u].add;
    tr[lc].add += tr[u].add;
    tr[rc].add += tr[u].add;
    tr[u].add = 0;
}
void add(int u, int l, int r, int k) {
    if (l > tr[u].r || r < tr[u].l) return;
    if (l <= tr[u].l && tr[u].r <= r) {
        tr[u].sum += k;
        tr[u].add += k;
        return;
    }
    pushdown(u);
    add(lc, l, r, k);
    add(rc, l, r, k);
    pushup(u);
}
void update(int u, int l, int r, int k) {
    if (l > tr[u].r || r < tr[u].l) return;
    if (l <= tr[u].l && tr[u].r <= r) {
        tr[u].sum = k;
        tr[u].add = 0;
        tr[u].ch = k;
        tr[u].vis = true;
        return;
    } 
    pushdown(u);
    update(lc, l, r, k);
    update(rc, l, r, k);
    pushup(u);
}
ll query(int u, int l, int r) {
    if (l > tr[u].r || r < tr[u].l) return -((ll)1 << 30);
    if (l <= tr[u].l && tr[u].r <= r) {
        return tr[u].sum;
    }
    pushdown(u);
    return max(query(lc, l, r), query(rc, l, r));
}
int main() {
    scanf("%d%d", &n, &q);
    for (int i = 1; i <= n; i++) {
        scanf("%d", &a[i]);      
    }
    build(1, 1, n);    
    while (q--) {
        int op, l, r, x;
        scanf("%d%d%d", &op, &l, &r);
        if (op == 1) {
            scanf("%d", &x);
            update(1, l, r, x);
        } else if (op == 2) {
            scanf("%d", &x);
            add(1, l, r, x);
        } else {
            printf("%lld\n", query(1, l, r));
        }
    }
    return 0;
}