func_code_string: #include <bits/stdc++.h>   #pragma comment(linker,  /STACK: 2000000 )   using namespace std;   int main(void) {     srand(time(0));     cout << fixed << setprecision(7);     cerr << fixed << setprecision(7);     int n;     ios_base ::sync_with_stdio(0);     cin.tie(0);     cin >> n;     function<int(int)> ok = [&](int k) {       return !k ? 0 : ok(k / 10) | ((k % 10 != 4) && (k % 10 != 7));     };     static int f[1 << 20];     for (int i = 1; i <= n; ++i) f[i] = i;     function<int(int)> get = [&](int k) {       return k == f[k] ? k : f[k] = get(f[k]);     };     for (int i = 1; i < n; ++i) {       int a, b, c;       cin >> a >> b >> c;       if (ok(c)) f[get(a)] = get(b);     }     static int S[1 << 20];     for (int i = 1; i <= n; ++i) ++S[get(i)];     long long ans = 0;     for (int i = 1; i <= n; ++i)       ans += 1ll * (n - S[get(i)]) * (n - S[get(i)] - 1);     cout << ans <<   n ;     return 0;   }   