#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int MaxN=50005;
inline int read(){char c;int rec=0,f=1;while((c=getchar())<'0'||c>'9')if(c=='-')f=-1;while(c>='0'&&c<='9')rec=rec*10+c-'0',c=getchar();return rec*f;
}
int n,m;
struct Branch {int next,to;}branch[100005];
int h[50005],cnt=0;
inline void add(int x,int y){branch[++cnt].to=y;branch[cnt].next=h[x];h[x]=cnt;return ;}
struct Lct_Tree{int F,s[2],val;long long lexp,rexp,sum,size;long long exp,rev,add;inline void NewNode(int x){F=s[0]=s[1]=0;size=1;val=lexp=rexp=sum=exp=x;rev=add=0;return ;}
}tree[50005];
inline void Dfs(int v,int pre){tree[v].F=pre;for(int i=h[v];i;i=branch[i].next){int j=branch[i].to;if(j==pre)continue;Dfs(j,v);}return ;
}
inline bool Isroot(int v){return tree[tree[v].F].s[0]!=v&&tree[tree[v].F].s[1]!=v;}
inline void Pushup(int v){tree[v].size=tree[tree[v].s[0]].size+1+tree[tree[v].s[1]].size;tree[v].sum=tree[tree[v].s[0]].sum+tree[v].val+tree[tree[v].s[1]].sum;tree[v].lexp=tree[tree[v].s[0]].lexp+tree[v].val*(tree[tree[v].s[0]].size+1)+tree[tree[v].s[1]].lexp+tree[tree[v].s[1]].sum*(tree[tree[v].s[0]].size+1);tree[v].rexp=tree[tree[v].s[1]].rexp+tree[v].val*(tree[tree[v].s[1]].size+1)+tree[tree[v].s[0]].rexp+tree[tree[v].s[0]].sum*(tree[tree[v].s[1]].size+1);tree[v].exp=tree[tree[v].s[0]].exp+tree[tree[v].s[1]].exp+(tree[tree[v].s[0]].size+1)*tree[tree[v].s[1]].rexp+(tree[tree[v].s[1]].size+1)*tree[tree[v].s[0]].lexp+tree[v].val*(tree[tree[v].s[0]].size+1)*(tree[tree[v].s[1]].size+1);return ;
}
inline void Rev(int v){if(v==0)return ;tree[v].rev^=1;swap(tree[v].s[0],tree[v].s[1]);swap(tree[v].lexp,tree[v].rexp);return ;
}
inline void Add(int v,int x){if(v==0)return ;tree[v].add+=x;tree[v].val+=x;tree[v].sum+=x*tree[v].size;tree[v].lexp+=x*tree[v].size*(tree[v].size+1)/2;tree[v].rexp+=x*tree[v].size*(tree[v].size+1)/2;tree[v].exp+=x*tree[v].size*(tree[v].size+1)*(tree[v].size+2)/6;return ;
}
inline void Pushdown(int v){if(tree[v].rev){Rev(tree[v].s[0]);Rev(tree[v].s[1]);tree[v].rev=0;}if(tree[v].add){Add(tree[v].s[0],tree[v].add);Add(tree[v].s[1],tree[v].add);tree[v].add=0;}return ;
}
inline void Lazy(int v){if(!Isroot(v))Lazy(tree[v].F);Pushdown(v);return ;}
inline void Rotate(int v){int p=tree[v].F,g=tree[p].F;int t1=v==tree[p].s[1],t2=p==tree[g].s[1],S=tree[v].s[1^t1];if(!Isroot(p))tree[g].s[t2]=v;tree[v].F=g;tree[p].s[t1]=S;tree[S].F=p;tree[v].s[1^t1]=p;tree[p].F=v;Pushup(p);return;
}
inline void Splay(int v){Lazy(v);while(!Isroot(v)){int p=tree[v].F,g=tree[p].F;if(!Isroot(p))(v==tree[p].s[1])^(p==tree[g].s[1])?Rotate(v):Rotate(p);Rotate(v);}Pushup(v);return;
}
inline void Access(int v){for(int temp=0;v;temp=v,v=tree[v].F){Splay(v);tree[v].s[1]=temp;Pushup(v);}return ;
}
inline void Make_Root(int v){Access(v);Splay(v);Rev(v);return ;}
inline int Find_Root(int v){while(tree[v].F)v=tree[v].F;return v;}
inline void Link(int v1,int v2){Make_Root(v1);tree[v1].F=v2;return ;}
inline void Cut(int v1,int v2){Make_Root(v1);Access(v2);Splay(v2);if(tree[v2].s[0]==v1&&tree[v1].s[1]==0){tree[v2].s[0]=tree[v1].F=0;Pushup(v2);}return ;
}
inline void Insert(int v1,int v2,int x){Make_Root(v1);Access(v2);Splay(v2);Add(v2,x);return ;}
inline long long Gcd(long long a,long long b){if(b==0)return a;return Gcd(b,a%b);}
inline void Print(int v){long long a=tree[v].exp,b=tree[v].size*(tree[v].size+1)>>1;long long d=Gcd(a,b);cout<<(a/d)<<'/'<<(b/d)<<'\n';return ;
}
inline void Ask(int v1,int v2){Make_Root(v1);Access(v2);Splay(v2);Print(v2);return ;}
int main(){n=read();m=read();for(int i=1;i<=n;i++)tree[i].NewNode(read());for(int i=1;i<n;i++){int x=read(),y=read();add(x,y);add(y,x);}Dfs(1,0);for(int i=1;i<=m;i++){int f=read(),x=read(),y=read();switch (f){case 1:{if(Find_Root(x)==Find_Root(y)&&x!=y)Cut(x,y);break;}case 2:{if(Find_Root(x)!=Find_Root(y))Link(x,y);break;}case 3:{int z=read();if(Find_Root(x)==Find_Root(y))Insert(x,y,z);break;}case 4:{if(Find_Root(x)==Find_Root(y))Ask(x,y);else cout<<-1<<'\n';break;}}}return 0;
}

更正式的题解哪天完全搞懂了，有时间的时候补上。就是Pushup里的一个乘号被写成了加号，眼瞎的蒟蒻选手一晚上才找出来。。。