#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void read(T &x) {
  x = 0;
  char c = getchar();
  int f = 1;
  while (!isdigit(c)) {
    if (c == '-') f = -1;
    c = getchar();
  }
  while (isdigit(c)) {
    x = x * 10 + c - '0';
    c = getchar();
  }
  x *= f;
}
template <class T>
inline void umin(T &x, T y) {
  x = x < y ? x : y;
}
template <class T>
inline void umax(T &x, T y) {
  x = x > y ? x : y;
}
inline unsigned int R() {
  static unsigned int seed = 416;
  return seed ^= seed >> 5, seed ^= seed << 17, seed ^= seed >> 13;
}
const int N = 366666;
int n, m;
vector<int> e[N];
long long res;
bool gg[N];
int val[N], lc[N], rc[N], lzy[N], dis[N], rt[N], tot;
vector<pair<int, int> > mrk[N];
inline void pushlzy(int k, int x) {
  if (k) val[k] += x, lzy[k] += x;
}
inline void pushdown(int k) {
  if (lzy[k]) pushlzy(lc[k], lzy[k]), pushlzy(rc[k], lzy[k]), lzy[k] = 0;
}
int merge(int x, int y) {
  if (!x || !y) return x + y;
  if (val[x] < val[y]) swap(x, y);
  pushdown(y);
  rc[y] = merge(x, rc[y]);
  if (dis[lc[y]] < dis[rc[y]]) swap(lc[y], rc[y]);
  dis[y] = dis[rc[y]] + 1;
  return y;
}
void dfs(int u, int fa) {
  for (register int i = (0); i <= (((int)e[u].size()) - 1); i++)
    if (e[u][i] != fa) dfs(e[u][i], u), rt[u] = merge(rt[u], rt[e[u][i]]);
  for (register int i = (0); i <= (((int)mrk[u].size()) - 1); i++)
    if (mrk[u][i].second > 0) {
      val[mrk[u][i].second] = mrk[u][i].first;
      rt[u] = merge(rt[u], mrk[u][i].second);
    }
  for (register int i = (0); i <= (((int)mrk[u].size()) - 1); i++)
    if (mrk[u][i].second < 0) gg[-mrk[u][i].second] = 1;
  while (rt[u] && gg[rt[u]]) rt[u] = merge(lc[rt[u]], rc[rt[u]]);
  if (fa && !rt[u]) {
    puts("-1");
    exit(0);
  }
  res += val[rt[u]];
  pushlzy(rt[u], -val[rt[u]]);
}
int main() {
  read(n);
  read(m);
  for (register int i = (1); i <= (n - 1); i++) {
    int u, v;
    read(u);
    read(v);
    e[u].push_back(v);
    e[v].push_back(u);
  }
  for (register int i = (1); i <= (m); i++) {
    int u, v, x;
    read(u);
    read(v);
    read(x);
    mrk[u].push_back(pair<int, int>(x, i));
    mrk[v].push_back(pair<int, int>(x, -i));
  }
  dfs(1, 0);
  cout << res;
  return 0;
}
