#include <iostream>
#include <cstdio>
#include <cassert>
#include <cstring>
#include <vector>
#include <valarray>
#include <array>
#include <queue>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <cmath>
#include <complex>
#include <random>

using namespace std;
typedef long long ll;
typedef pair<int, int> P;

struct Tree {
    typedef Tree* NP;
    NP l, r;
    struct Node {
        Node(int sz) : sz(sz) {}
        int sz;
        int d, sm, lz;
        int lsm, rsm, ma, mv;
        bool lzf;
    } n;

    void lzdata(int d) {
        n.d = n.mv = d;
        n.sm = n.sz*d;
        n.lsm = n.rsm = n.ma = max(0, n.sm);
        n.lz = d;
        n.lzf = true;
    }
    void push() {
        if (n.sz == 1) return;
        if (n.lzf) {
            l->lzdata(n.lz);
            r->lzdata(n.lz);
            n.lzf = false;
        }
    }
    static Node merge(Node l, Node r) {
        if (l.sz == 0) return r;
        if (r.sz == 0) return l;
        Node res(l.sz + r.sz);
        res.sm = l.sm+r.sm;
        res.lsm = max(l.lsm, l.sm+r.lsm);
        res.rsm = max(r.rsm, r.sm+l.rsm);
        res.ma = max(max(l.ma, r.ma), l.rsm+r.lsm);
        res.mv = max(l.mv, r.mv);
        res.lzf = false;
        return res;
    }
    static Node rev(Node u) {
        swap(u.lsm, u.rsm);
        return u;
    }
    Tree(int sz, int hev[]) : n(sz) {
        l = r = nullptr;
        if (sz == 1) return;
        int sm = 0;
        for (int i = 0; i < sz; i++) {
            sm += hev[i];
        }
        int md = 0;
        int sm2 = 0;
        for (md = 0; md < sz-1; md++) {
            if (sm2*2 >= sm) break;
            sm2 += hev[md];
        }
        l = new Tree(md, hev);
        r = new Tree(sz - md, hev+md);
    }
    void set(int k, int x) {
//        printf("set %d %d\n", k, x);
        if (n.sz == 1) {
            lzdata(x);
            return;
        }
        push();
        if (k < l->n.sz) {
            l->set(k, x);
        } else {
            r->set(k - l->n.sz, x);
        }
        n = merge(l->n, r->n);
    }
    void set(int a, int b, int x) {
        if (b <= 0 || n.sz <= a) {
            return;
        }
        push();
        if (a <= 0 && n.sz <= b) {
            lzdata(x);
            return;
        }
        l->set(a, b, x);
        r->set(a - l->n.sz, b - l->n.sz, x);
        n = merge(l->n, r->n);
    }
    Node get(int a, int b) {
        if (b <= 0 || n.sz <= a) {
            return Node(0);
        }
        push();
        if (a <= 0 && n.sz <= b) {
            return n;
        }
        return merge(l->get(a, b), r->get(a- l->n.sz, b- l->n.sz));
    }
};

template <int N>
struct HLComp_Y {
    vector<int> g[N];

    P n2l[N]; //node to line (line id - line pos)
    int lc;
    Tree *li[N]; //line data
    P l2p[N]; //line to parent
    int sz[N]; //node size

    int buf[N]; // buffer of sz - sz[child]
    int ldps[N]; // line dps
    void add(int a, int b) {
        g[a].push_back(b);
        g[b].push_back(a);
    }
    void dfs_sz(int p, int b) {
        sz[p] = 1;
        for (int d: g[p]) {
            if (d == b) continue;
            dfs_sz(d, p);
            sz[p] += sz[d];
        }
    }
    void dfs(int p, int b) {
        if (g[p].size() == (b == -1 ? 0 : 1)) {
            // make line
            li[n2l[p].first] = new Tree(n2l[p].second+1, buf);
            return;
        }
        int ma = -1, md = -1;
        for (int d: g[p]) {
            if (d == b) continue;
            if (ma < sz[d]) {
                ma = sz[d];
                md = d;
            }
        }
        for (int d: g[p]) {
            if (d == b) continue;
            if (d == md) {
                //heavy
                n2l[d] = P(n2l[p].first, n2l[p].second+1);
                buf[n2l[p].second] = sz[p]-sz[d];
                dfs(md, p);
            } else {
                //light
                n2l[d] = P(lc, 0);
                l2p[lc] = n2l[p];
                ldps[lc] = ldps[n2l[p].first]+1;
                lc++;
            }
        }
        for (int d: g[p]) {
            if (d == b) continue;
            if (d == md) continue;
            dfs(d, p); // light
        }
    }
    void init() {
        n2l[0] = P(0, 0);
        l2p[0] = P(-1, 0);
        ldps[0] = 0;
        lc = 1;
        dfs_sz(0, -1);
        dfs(0, -1);
    }
    void data_set(int k, int x) {
        li[n2l[k].first]->set(n2l[k].second, x);
    }
    void path_set(int u, int v, int d) {
        int xl, xp; tie(xl, xp) = n2l[u];
        int yl, yp; tie(yl, yp) = n2l[v];
        if (ldps[xl] > ldps[yl]) {
            while (ldps[xl] > ldps[yl]) {
                li[xl]->set(0, xp+1, d);
                tie(xl, xp) = l2p[xl];
            }
        } else if (ldps[xl] < ldps[yl]) {
            while (ldps[xl] < ldps[yl]) {
                li[yl]->set(0, yp+1, d);
                tie(yl, yp) = l2p[yl];
            }
        }
        while (xl != yl) {
            assert(ldps[xl] == ldps[yl]);
            li[xl]->set(0, xp+1, d);
            tie(xl, xp) = l2p[xl];

            li[yl]->set(0, yp+1, d);
            tie(yl, yp) = l2p[yl];
        }
        if (xp > yp) {
            li[xl]->set(yp, xp+1, d);
        } else {
            li[yl]->set(xp, yp+1, d);
        }   
    }
    Tree::Node path_get(int u, int v) {
        int xl, xp; tie(xl, xp) = n2l[u];
        int yl, yp; tie(yl, yp) = n2l[v];
        Tree::Node nl(0), nr(0);
        if (ldps[xl] > ldps[yl]) {
            while (ldps[xl] > ldps[yl]) {
                nl = Tree::merge(li[xl]->get(0, xp+1), nl);
                tie(xl, xp) = l2p[xl];
            }
        } else if (ldps[xl] < ldps[yl]) {
            while (ldps[xl] < ldps[yl]) {
                nr = Tree::merge(li[yl]->get(0, yp+1), nr);
                tie(yl, yp) = l2p[yl];
            }
        }
        while (xl != yl) {
            assert(ldps[xl] == ldps[yl]);
            nl = Tree::merge(li[xl]->get(0, xp+1), nl);
            tie(xl, xp) = l2p[xl];
            nr = Tree::merge(li[yl]->get(0, yp+1), nr);
            tie(yl, yp) = l2p[yl];
        }
        if (xp > yp) {
            nl = Tree::merge(li[xl]->get(yp, xp+1), nl);
        } else {
            nr = Tree::merge(li[yl]->get(xp, yp+1), nr);
        }
        nl = Tree::rev(nl);
        return Tree::merge(nl, nr);
    }
};

const int MN = 200100;
HLComp_Y<MN> hl;

int w[MN];
int main2() {
    int n, q;
    scanf("%d %d", &n, &q); //# of node
    for (int i = 0; i < n; i++) {
        scanf("%d", w+i);
    }
    for (int i = 0; i < n-1; i++) {
        int s, e;
        scanf("%d %d", &s, &e); s--; e--;
        hl.add(s, e);
    }
    hl.init();
    for (int i = 0; i < n; i++) {
        hl.data_set(i, w[i]);
    }
    for (int i = 0; i < q; i++) {
        int t, a, b, c;
        scanf("%d %d %d %d", &t, &a, &b, &c); a--; b--;
        if (t == 1) {
            hl.path_set(a, b, c);
        } else {
            auto n = hl.path_get(a, b);
            printf("%d\n", (n.mv < 0) ? n.mv : n.ma);
        }
    }
    return 0;
}


/*AOJ??¨ stack size???????????????*/
int main() {
#ifndef __APPLE__
    static ll eord, enew;
    const int sz = 32*1024*1024;
    static void *p = malloc(sz);
    enew = (long long)p + sz - 1;
    __asm__ volatile("mov %%rsp, %0" : "=r"(eord));
    __asm__ volatile("mov %0, %%rsp" : : "r"(enew));
#endif
    main2();
#ifndef __APPLE__
    __asm__ volatile("mov %0, %%rsp" : : "r"(eord));
#endif

    return 0;
}

Measured memory_bytes: 63848