func_code_string: #include <bits/stdc++.h>   using namespace std;   template <class n, class second>   ostream &operator<<(ostream &p, pair<n, second> x) {     return p <<  <  << x.first <<  ,   << x.second <<  > ;   }   template <class n>   auto operator<<(ostream &p, n y) ->       typename enable_if<!is_same<n, string>::value,                          decltype(y.begin(), p)>::type {     int o = 0;     p <<  { ;     for (auto c : y) {       if (o++) p <<  ,  ;       p << c;     }     return p <<  } ;   }   void dor() { cerr << endl; }   template <class n, class... second>   void dor(n p, second... y) {     cerr << p <<    ;     dor(y...);   }   template <class n, class second>   void mini(n &p, second y) {     if (p > y) p = y;   }   template <class n, class second>   void maxi(n &p, second y) {     if (p < y) p = y;   }   const int M = 1024 * 256;   int n, k, x;   int in[M];   int main() {     scanf( %d%d , &n, &k);     for (int i = (2); i <= (int)(n); ++i) {       int a, b;       scanf( %d%d , &a, &b);       in[a]++;       in[b]++;     }     for (int i = (1); i <= (int)(n); ++i) {       if (in[i] == 1) {         x++;       }     }     printf( %.9Lf n , (long double)(k * 2) / x);     return 0;   }   