#include <bits/stdc++.h> using namespace std; #define int long long const int maxn = 1e4 + 5; vector<pair<int, int>> adj[maxn]; int sz[maxn], sum[maxn], n, k, x; void minimize(int &a, int b){ a = min(a, b); } vector<array<int, 2>> dfs(int u, int p) { sz[u] = 1; vector<array<int, 2>> dp(n + 1, array<int, 2>{10000000000, 10000000000}); dp[1][0] = dp[0][0] = 0; dp[1][1] = -sum[u]; for(auto [v, w]: adj[u]){ if(v == p) continue; sum[v] = sum[u] + w; vector<array<int, 2>> ndp = dfs(v, u); for(int i = sz[u]; i >= 0; i--){ for(int j = 0; j <= sz[v]; j++) { int add = 2 * w * (j > 0); minimize(dp[i + j][0], dp[i][0] + ndp[j][0] + add); minimize(dp[i + j][1], min(dp[i][0] + ndp[j][1], dp[i][1] + ndp[j][0]) + add); } } sz[u] += sz[v]; } dp.resize(sz[u] + 1); return dp; } void solve(){ cin >> n >> k >> x; for (int i = 1; i <= n - 1; i++){ int u, v, w; cin >> u >> v >> w; adj[u].push_back({v, w}); adj[v].push_back({u, w}); } cout << dfs(x, 0)[k][1]; } signed main() { ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); solve(); }