func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MAX = 2e5 + 6;   const long long MOD = 1e9 + 7;   int par[MAX];   long long sz[MAX];   long long triplets(long long x) { return x * (x - 1) * (x - 2); }   bool isLucky(long long x) {     while (x) {       if (x % 10 != 4 and x % 10 != 7) return false;       x /= 10;     }     return true;   }   int Find(int u) {     if (u == par[u]) return u;     return par[u] = Find(par[u]);   }   void Union(int u, int v) {     u = Find(u);     v = Find(v);     if (sz[u] < sz[v]) swap(u, v);     if (u != v) {       par[v] = u;       sz[u] += sz[v];     }   }   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     long long n;     cin >> n;     for (int i = 1; i <= n; i++) par[i] = i, sz[i] = 1;     for (int i = 1; i <= n - 1; i++) {       long long u, v, w;       cin >> u >> v >> w;       if (!isLucky(w)) Union(u, v);     }     long long ans = n * (n - 1) * (n - 2);     for (int i = 1; i <= n; i++) {       if (Find(i) == i) {         ans -= 2 * sz[i] * (sz[i] - 1) * (n - sz[i]) +                sz[i] * (sz[i] - 1) * (sz[i] - 2);       }     }     cout << ans;   }   