#include <bits/stdc++.h>
using namespace std;
const int MAXN = 300005;
const int MAXINT = 1073741823;
vector<long long int> neighbors[MAXN];
vector<pair<long long int, long long int>> queries[MAXN];
set<pair<long long int, long long int>> availables[MAXN];
long long int height[MAXN], result[MAXN], others[MAXN];
void dfs(long long int v, long long int parent, long long int level) {
  height[v] = level;
  long long int children_sum = 0;
  for (long long int i : neighbors[v])
    if (i != parent) {
      dfs(i, v, level + 1);
      if (result[i] < 0) {
        result[v] = -MAXINT;
        return;
      }
      children_sum += result[i];
    }
  for (long long int i : neighbors[v])
    if (i != parent) {
      others[i] += children_sum - result[i];
      if (availables[v].size() < availables[i].size()) {
        availables[v].swap(availables[i]);
        swap(others[v], others[i]);
      }
      for (pair<long long int, long long int> j : availables[i])
        availables[v].emplace(j.first + others[i] - others[v], j.second);
    }
  for (pair<long long int, long long int> j : queries[v])
    availables[v].emplace(j.second + children_sum - others[v], height[j.first]);
  while (!availables[v].empty() && (*availables[v].begin()).second >= height[v])
    availables[v].erase(availables[v].begin());
  result[v] =
      (availables[v].empty() ? -MAXINT
                             : (*availables[v].begin()).first + others[v]);
  return;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  long long int n, m, u, v, c, answer = 0;
  cin >> n >> m;
  for (long long int i = 0; i < n - 1; i++) {
    cin >> u >> v;
    u--;
    v--;
    neighbors[u].push_back(v);
    neighbors[v].push_back(u);
  }
  for (long long int i = 0; i < m; i++) {
    cin >> u >> v >> c;
    u--;
    v--;
    queries[u].emplace_back(v, c);
  }
  dfs(0, 0, 0);
  for (long long int i : neighbors[0])
    if (result[i] < 0) {
      cout << -1;
      return 0;
    } else
      answer += result[i];
  cout << answer;
  return 0;
}
