#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define MAXN 1000005
#define Inf 1000000000000000000ll
ll w[MAXN * 4], a[MAXN], lzy_add[MAXN * 4], lzy_set[MAXN * 4];
int n, q;
bool InRange(int L, int R, int l, int r)
{
    return (L >= l) && (R <= r);
}
bool OutofRange(int L, int R, int l, int r)
{
    return (L > r) | (R < l);
}
void pushup(int u)
{
    w[u] = max(w[u * 2], w[u * 2 + 1]);
}
void build(int u, int L, int R)
{
    lzy_set[u] = Inf;
    if (L == R)
    {
        w[u] = a[L];
    }
    else
    {
        int M = (L + R) / 2;
        build(u * 2, L, M);
        build(u * 2 + 1, M + 1, R);
        pushup(u);
    }
}
void maketag(int u, ll x, int type)
{
    if (type == 1)
    {
        lzy_add[u] = 0;
        lzy_set[u] = x;
        w[x] = x;
    }
    else
    {
        if (lzy_set[u] == Inf)
        {
            lzy_add[u] += x;
        }
        else
        {
            lzy_set[u] += x;
            w[u] += x;
        }
    }
}
void pushdown(int u)
{
    if (lzy_set[u] == Inf)
    {
        maketag(u * 2, lzy_add[u], 2);
        maketag(u * 2 + 1, lzy_add[u], 2);
        lzy_add[u] = 0;
    }
    else
    {
        maketag(u * 2, lzy_set[u], 1);
        maketag(u * 2 + 1, lzy_set[u], 1);
        lzy_set[u] = Inf;
    }
}
void update1(int u, int L, int R, int l, int r, ll x)
{
    if (InRange(L, R, l, r))
    {
        maketag(u, x, 1);
    }
    else if (!OutofRange(L, R, l, r))
    {
        int M = (L + R) / 2;
        pushdown(u);
        update1(u * 2, L, M, l, r, x);
        update1(u * 2 + 1, M + 1, R, l, r, x);
        pushup(u);
    }
    else
    {
        return;
    }
}
void update2(int u, int L, int R, int l, int r, ll x)
{
    if (InRange(L, R, l, r))
    {
        maketag(u, x, 2);
    }
    else if (!OutofRange(L, R, l, r))
    {
        int M = (L + R) / 2;
        pushdown(u);
        update2(u * 2, L, M, l, r, x);
        update2(u * 2 + 1, M + 1, R, l, r, x);
        pushup(u);
    }
    else
    {
        return;
    }
}
ll query(int u, int L, int R, int l, int r)
{
    if (InRange(L, R, l, r))
    {
        return max(w[u * 2], w[u * 2 + 1]);
    }
    else if (!OutofRange(L, R, l, r))
    {
        int M = (L + R) / 2;
        pushdown(u);
        return max(query(u * 2, L, M, l, r), query(u * 2 + 1, M + 1, R, l, r));
    }
    else
    {
        return -1000000000000000000ll;
    }
}
int main()
{
    cin >> n >> q;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
    }
    build(1, 1, n);
    int op, x, y, z;
    for (int i = 1; i <= q; i++)
    {
        cin >> op;
        if (op == 1)
        {
            cin >> x >> y >> z;
            update1(1, 1, n, x, y, z);
        }
        else if (op == 2)
        {
            cin >> x >> y >> z;
            update2(1, 1, n, x, y, z);
        }
        else
        {
            cin >> x >> y;
            cout << query(1, 1, n, x, y) << endl;
        }
    }
    return 0;
}