#include<bits/stdc++.h>
#define ll long long
#define pb emplace_back
#define N 300010
using namespace std;
struct nod{int l,r,y;ll v,ta;}t[N];
vector<int> a[N];
int rt[N],m,n,x,y,d[N],p;
void jb(int x,int y){a[x].pb(y);}
void ya(int x){if (t[x].ta){t[x].v+=t[x].ta;t[t[x].l].ta+=t[x].ta;t[t[x].r].ta+=t[x].ta;t[x].ta=0;}}
int me(int x,int y){
	if (!x||!y) return x|y;
	ya(x);ya(y);
	if (t[x].v>t[y].v) swap(x,y);
	if(rand()%2)swap(t[x].l,t[x].r);
	t[x].r=me(t[x].r,y);
	return x;
}
void dfs(int x,int fa){
	d[x]=d[fa]+1;
	ll mi=0;
	for (auto y:a[x]){
		if (y!=fa){
			dfs(y,x);
			while (d[t[rt[y]].y]>d[x])rt[y]=me(t[rt[y]].l,t[rt[y]].r);
			if (rt[y]==0)p=1;
			mi+=t[rt[y]].v;
		}
	}
	t[rt[x]].ta+=mi;
	for (auto y:a[x]){if (y!=fa){t[rt[y]].ta+=mi-t[rt[y]].v;rt[x]=me(rt[x],rt[y]);}}
}
int main(){
	cin>>n>>m;
	for (int i=1;i<n;i++){cin>>x>>y;jb(x,y);jb(y,x);}
	for (int i=1;i<=m;i++){cin>>x>>t[i].y>>t[i].v;if (x!=t[i].y)rt[x]=me(rt[x],i);}
	dfs(1,0);
	if (p)puts("-1");else {ya(rt[1]);cout<<t[rt[1]].v<<endl;}
	return 0;
}