func_code_string: #include <bits/stdc++.h>   using namespace std;   inline bool is_palindrome(const string& s) {     return std::equal(s.begin(), s.end(), s.rbegin());   }   const long long MOD = 1000000007;   const long long INF = 1e9 + 5;   const double eps = 1e-7;   const double PI = acos(-1.0);   inline void debug_vi(vector<int> a) {     for (long long i = (long long)(0); i < (long long)(a.size()); i++)       cout << a[i] <<    ;   }   inline void debug_vll(vector<long long> a) {     for (long long i = (long long)(0); i < (long long)(a.size()); i++)       cout << a[i] <<    ;   }   const int N = 1e5 + 5;   int in[N];   int main() {     std::ios::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     int n, s, a, b;     cin >> n >> s;     memset(in, 0, sizeof(in));     for (long long i = (long long)(0); i < (long long)(n - 1); i++) {       cin >> a >> b;       a--;       b--;       in[a]++;       in[b]++;     }     int l = 0;     for (long long i = (long long)(0); i < (long long)(n); i++) {       if (in[i] == 1) {         l++;       }     }     double ans = 2.0 * s / l;     cout << fixed << showpoint << setprecision(15) << ans;     ;     return 0;   }   