#define NDEBUG

#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>
#include <map>
#include <queue>
#include <set>
#include <tuple>
#include <cassert>

using namespace std;
  
typedef long long ll;
struct LCNode {
    typedef LCNode* NP;
    typedef int D;
    static const int INF = 1LL<<25;
    static const int DF = 1LL<<25;
    static LCNode last_d;
    static NP last;
    NP p, l, r;
    int sz;
    int v, sm, lz;
    int lsm, rsm, ma, mv;
    bool rev;
    LCNode(D v) :p(NULL), l(last), r(last), sz(1),
        v(v), sm(v), lz(DF), rev(false),
        lsm(max(v, 0)), rsm(max(v, 0)), ma(max(v, 0)), mv(v) {}
    LCNode() : l(NULL), r(NULL), sz(0), v(-INF), mv(-INF) {}
    inline int pos() {
        if (p) {
            if (p->l == this) return -1;
            if (p->r == this) return 1;
        }
        return 0;
    }
    void rot() {
        NP qq = p->p;
        //p->push(); push();
        int qp = p->pos();
        if (p->l == this) {
            p->l = r; r->p = p;
            r = p; p->p = this;
        } else {
            p->r = l; l->p = p;
            l = p; p->p = this;
        }
        p->update(); update();
        p = qq;
        if (!qp) return;
        if (qp == -1) {
            qq->l = this;
        } else {
            qq->r = this;
        }
        qq->update();
    }
    void splay() {
        assert(this != last);
        supush();
        int ps;
        while ((ps = pos())) {
            int pps = p->pos();
            if (!pps) {
                rot();
            } else if (ps == pps) {
                p->rot(); rot();
            } else {
                rot(); rot();
            }
        }
    }
    void expose() {
        assert(this != last);
        NP u = this;
        do {
            u->splay();
        } while ((u = u->p));
        u = last;
        u->p = this;
        do {
            u->p->r = u;
            u->p->update();
            u = u->p;
        } while (u->p);
        splay();
    }
    void push() {
        if (rev) {
            if (l->sz) {
                l->revdata();
            }
            if (r->sz) {
                r->revdata();
            }
            rev = false;
        }
        if (lz != DF) {
            if (l->sz) {
                l->lzdata(lz);
            }
            if (r->sz) {
                r->lzdata(lz);
            }
            lz = DF;
        }
    }
    void supush() {
        if (pos()) {
            p->supush();
        }
        push();
    }
    void revdata() {
        assert(this != last);
        swap(l, r);
        swap(lsm, rsm);
        rev ^= true;
    }
    void lzdata(D d) {
        assert(this != last);
        v = mv = d;
        sm = sz*d;
        lsm = rsm = ma = max(0, sm);
        lz = d;
    }
    NP update() {
        assert(this != last);
        sz = 1+l->sz+r->sz;
        sm = v+l->sm+r->sm;
        lsm = max(l->lsm, l->sm+v+r->lsm);
        rsm = max(r->rsm, r->sm+v+l->rsm);
        ma = max(l->ma, r->ma);
        ma = max(ma, l->rsm+v+r->lsm);
        mv = max(l->mv, r->mv);
        mv = max(mv, v);
        return this;
    }

    void evert() {
        expose();
        revdata();
    }
};
LCNode LCNode::last_d = LCNode();
LCNode::NP LCNode::last = &last_d;
 

const int MN = 201000;
LCNode tr[MN];
int main() {
    int n, q;
    scanf("%d %d", &n, &q);
    for (int i = 0; i < n; i++) {
        int w;
        scanf("%d", &w);
        tr[i] = LCNode(w);
    }
    for (int i = 0; i < n-1; i++) {
        int s, e;
        scanf("%d%d", &s, &e); s--; e--;
        tr[s].evert();
        tr[e].expose();
        tr[s].p = &tr[e];
    }
    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) {
            tr[a].evert();
            tr[b].expose();
            tr[b].lzdata(c);
        } else {
            tr[a].evert();
            tr[b].expose();
            int d;
            if (tr[b].mv < 0) d = tr[b].mv;
            else d = tr[b].ma;
            printf("%d\n", d);
        }
    }
}

Measured memory_bytes: 13740