#include <iostream>

struct Node {
    long long v;
    long long lazy;
    long long chg;
    bool jud;
};

int n = 0;
long long num[1000005] = {};
Node tr[4000005] = {};

void pushdown(int p)
{
    int ls = p * 2, rs = p * 2 + 1;
    if (tr[p].jud) {
        tr[ls].v = tr[rs].v = tr[p].v;
        tr[ls].chg = tr[rs].chg = tr[p].chg + tr[p].lazy;
        tr[ls].jud = tr[rs].jud = true;
        tr[ls].lazy = tr[rs].lazy = 0;
    } else {
        tr[ls].v += tr[p].lazy;
        tr[rs].v += tr[p].lazy;
        tr[ls].lazy += tr[p].lazy;
        tr[rs].lazy += tr[p].lazy;
    }
    tr[p].lazy = 0;
    tr[p].chg = 0;
    tr[p].jud = false;
}

void pushup(int p)
{
    int ls = p * 2, rs = p * 2 + 1;
    tr[p].v = std::max(tr[ls].v, tr[rs].v);
}

void build(int l, int r, int p)
{
    tr[p].v = 0;
    tr[p].lazy = 0;
    tr[p].chg = 0;
    tr[p].jud = false;
    if (l == r) {
        tr[p].v = num[l];
        return;
    }

    int ls = p * 2, rs = p * 2 + 1;
    int mid = (l + r) >> 1;
    build(l, mid, ls);
    build(mid + 1, r, rs);
    pushup(p);
}

void change(int l, int r, int p, int x, int y, long long v)
{
    if (l > y || r < x) {
        return;
    }
    if (l >= x && r <= y) {
        tr[p].lazy = 0;
        tr[p].jud = true;
        tr[p].chg = v;
        tr[p].v = v;
        return;
    }

    pushdown(p);
    int ls = p * 2, rs = p * 2 + 1;
    int mid = (l + r) >> 1;
    change(l, mid, ls, x, y, v);
    change(mid + 1, r, rs, x, y, v);
    pushup(p);
}

void add(int l, int r, int p, int x, int y, long long v)
{
    if (l > y || r < x) {
        return;
    }
    if (l >= x && r <= y) {
        tr[p].lazy += v;
        tr[p].v += v;
        return;
    }

    pushdown(p);
    int ls = p * 2, rs = p * 2 + 1;
    int mid = (l + r) >> 1;
    add(l, mid, ls, x, y, v);
    add(mid + 1, r, rs, x, y, v);
    pushup(p);
}

long long ask(int l, int r, int p, int x, int y)
{
    if (l > y || r < x) {
        return 0;
    }
    if (l >= x && r <= y) {
        return tr[p].v;
    }

    pushdown(p);
    int ls = p * 2, rs = p * 2 + 1;
    int mid = (l + r) >> 1;
    return std::max(ask(l, mid, ls, x, y), ask(mid + 1, r, rs, x, y));
}

int main()
{
    int q = 0;
    scanf("%d%d", &n, &q);
    for (int i = 1; i <= n; ++i) {
        scanf("%lld", &num[i]);
    }

    build(1, n, 1);

    while (q--) {
        int op = 0;
        int l = 0, r = 0;
        int x = 0;
        scanf("%d", &op);
        scanf("%d%d", &l, &r);
        if (op != 3) {
            scanf("%d", &x);
        }
        if (op == 1) {
            change(1, n, 1, l, r, x);
        } else if (op == 2) {
            add(1, n, 1, l, r, x);
        } else {
            printf("%lld\n", ask(1, n, 1, l, r));
        }
    }

    return 0;
}