#include<bits/stdc++.h>
using namespace std;
using Int = long long;

struct HLDecomposition {
  int n,pos;
  vector<vector<int> > G;
  vector<int> vid, head, sub, hvy, par, dep, inv, type;
  
  HLDecomposition(){}
  HLDecomposition(int sz):
    n(sz),pos(0),G(n),
    vid(n,-1),head(n),sub(n,1),hvy(n,-1),
    par(n),dep(n),inv(n),type(n){}
  
  void add_edge(int u, int v) {
    G[u].push_back(v);
    G[v].push_back(u);
  }

  void build(vector<int> rs={0}) {
    int c=0;
    for(int r:rs){
      dfs(r);
      bfs(r, c++);
    }
  }
  
  void dfs(int rt) {
    using T = pair<int, int>;
    stack<T> st;
    par[rt]=-1;
    dep[rt]=0;
    st.emplace(rt,0);
    while(!st.empty()){
      int v=st.top().first;
      int &i=st.top().second;
      if(i<(int)G[v].size()){
	int u=G[v][i++];
	if(u==par[v]) continue;
	par[u]=v;
	dep[u]=dep[v]+1;
	st.emplace(u,0);
      }else{
	st.pop();
	int res=0;
	for(int u:G[v]){
	  if(u==par[v]) continue;
	  sub[v]+=sub[u];
	  if(res<sub[u]) res=sub[u],hvy[v]=u;
	}
      }
    }
  }

  void bfs(int r,int c) {
    int &k=pos;
    queue<int> q({r});
    while(!q.empty()){
      int h=q.front();q.pop();
      for(int i=h;i!=-1;i=hvy[i]) {
	type[i]=c;
	vid[i]=k++;
	inv[vid[i]]=i;
	head[i]=h;
	for(int j:G[i])
	  if(j!=par[i]&&j!=hvy[i]) q.push(j);
      }
    }
  }
  
  // for_each(vertex)
  // [l,r] <- attention!!
  void for_each(int u, int v, const function<void(int, int)>& f) {
    while(1){
      if(vid[u]>vid[v]) swap(u,v);
      f(max(vid[head[v]],vid[u]),vid[v]);
      if(head[u]!=head[v]) v=par[head[v]];
      else break;
    }
  }
  
  // for_each(edge)
  // [l,r] <- attention!!
  void for_each_edge(int u, int v, const function<void(int, int)>& f) {
    while(1){
      if(vid[u]>vid[v]) swap(u,v);
      if(head[u]!=head[v]){
	f(vid[head[v]],vid[v]);
        v=par[head[v]];
      } else{
	if(u!=v) f(vid[u]+1,vid[v]);
	break;
      }
    }
  }

  int lca(int u,int v){
    while(1){
      if(vid[u]>vid[v]) swap(u,v);
      if(head[u]==head[v]) return u;
      v=par[head[v]];
    }
  }

  int distance(int u,int v){
    return dep[u]+dep[v]-2*dep[lca(u,v)];
  }
};


template <typename T,typename E>
struct SegmentTree{
  typedef function<T(T,T)> F;
  typedef function<T(T,E)> G;
  typedef function<E(E,E)> H;
  typedef function<E(E,int)> P;
  int n;
  F f;
  G g;
  H h;
  P p;
  T d1;
  E d0;
  vector<T> dat;
  vector<E> laz;
  SegmentTree(int n_,F f,G g,H h,T d1,E d0,
	      vector<T> v=vector<T>(),P p=[](E a,int b){return a;}):
    f(f),g(g),h(h),d1(d1),d0(d0),p(p){
    init(n_);
    if(n_==(int)v.size()) build(n_,v);
  }
  void init(int n_){
    n=1;
    while(n<n_) n*=2;
    dat.clear();
    dat.resize(2*n-1,d1);
    laz.clear();
    laz.resize(2*n-1,d0);
  }
  void build(int n_, vector<T> v){
    for(int i=0;i<n_;i++) dat[i+n-1]=v[i];
    for(int i=n-2;i>=0;i--)
      dat[i]=f(dat[i*2+1],dat[i*2+2]);
  }
  inline void eval(int len,int k){
    if(laz[k]==d0) return;
    if(k*2+1<n*2-1){
      laz[k*2+1]=h(laz[k*2+1],laz[k]);
      laz[k*2+2]=h(laz[k*2+2],laz[k]);
    }
    dat[k]=g(dat[k],p(laz[k],len));
    laz[k]=d0;
  }
  T update(int a,int b,E x,int k,int l,int r){
    eval(r-l,k);
    if(r<=a||b<=l) return dat[k];
    if(a<=l&&r<=b){
      laz[k]=h(laz[k],x);
      return g(dat[k],p(laz[k],r-l));
    }
    return dat[k]=f(update(a,b,x,k*2+1,l,(l+r)/2),
		    update(a,b,x,k*2+2,(l+r)/2,r));
  }
  T update(int a,int b,E x){
    return update(a,b,x,0,0,n);
  }
  T query(int a,int b,int k,int l,int r){
    eval(r-l,k);
    if(r<=a||b<=l) return d1;
    if(a<=l&&r<=b) return dat[k];
    T vl=query(a,b,k*2+1,l,(l+r)/2);
    T vr=query(a,b,k*2+2,(l+r)/2,r);
    return f(vl,vr);
  }
  T query(int a,int b){
    return query(a,b,0,0,n);
  }
};


signed main(){
  int n,q;
  scanf("%d %d",&n,&q);
  HLDecomposition hld(n);
  vector<int> w(n);
  for(int i=0;i<n;i++) cin>>w[i];
  using P = pair<int,int>;
  for(int i=0;i<n-1;i++){
    int a,b;
    cin>>a>>b;
    a--;b--;
    hld.add_edge(a,b);
  }
  hld.build();
  
  using T = tuple<int,int,int,int,int,int,int>;
  
  T d1(-1,-1,-1,-1,-1,-1,-1);
  P d0(-1,-114514);

  auto &par=hld.par;
  auto &vid=hld.vid;;
  auto con=[&](int a,int b){
    return par[a]==b||par[b]==a;
  };
  
  auto f=[&](T a,T b){
    if(a>b) swap(a,b);
    
    if(get<0>(a)<0) return b;
    if(con(get<0>(a),get<1>(b))) swap(a,b);
   
    int al,ar,as,ava,avi,avl,avr;
    tie(al,ar,as,ava,avi,avl,avr)=a;
    int bl,br,bs,bva,bvi,bvl,bvr;
    tie(bl,br,bs,bva,bvi,bvl,bvr)=b;

    if(con(al,bl)||con(al,br)){
      swap(al,ar);
      swap(avl,avr);
    }
    if(con(ar,br)){
      swap(bl,br);
      swap(bvl,bvr);
    }
    if(!con(ar,bl)) return d1;
    
    int cl=al,cr=br,cs=as+bs;
    int cva=ava+bva,cvi=max(avi,bvi),cvl=avl,cvr=bvr;
    cvi=max(cvi,avr+bvl);
    cvl=max(cvl,ava+bvl);
    cvr=max(cvr,avr+bva);
    
    return T(cl,cr,cs,cva,cvi,cvl,cvr);
  };
  
  auto g=[&](T a,P p){
    int al,ar,as,ava,avi,avl,avr;
    tie(al,ar,as,ava,avi,avl,avr)=a;
    int v=p.first,b=p.second;
    if(~v) al=ar=v,as=1;
    if(b>=0) return T(al,ar,as,b*as,b*as,b*as,b*as);
    return T(al,ar,as,b*as,b,b,b);
  };
  
  auto h=[&](P a,P b){return b;};

  vector<T> vt(n);
  for(int i=0;i<n;i++)
    vt[vid[i]]=g(d1,P(i,w[i]));

  SegmentTree<T,P> seg(n,f,g,h,d1,d0,vt);
  
  while(q--){
    int t,a,b,c;
    scanf("%d %d %d %d",&t,&a,&b,&c);
    a--;b--;
    if(t==1){
      hld.for_each(a,b,[&](int l,int r){
	  seg.update(l,r+1,P(-1,c));
	});
    }
    if(t==2){
      vector<T> v;
      auto merge=[&](T x){
	for(int i=0;i<(int)v.size();i++){
	  T y=f(v[i],x);
	  if(~get<0>(y)){
	    v[i]=y;
	    return;
	  }
	}
	v.push_back(x);
      };
      hld.for_each(a,b,[&](int l,int r){merge(seg.query(l,r+1));});
      
      while(v.size()>1){
	T x=v.back();v.pop_back();
	merge(x);
      }
      
      int vl,vr,vs,vva,vvi,vvl,vvr;
      tie(vl,vr,vs,vva,vvi,vvl,vvr)=v.front();
      printf("%d\n",max({vva,vvi,vvl,vvr}));
    }
  }
  
  return 0;
}

Measured memory_bytes: 57356