#include <bits/stdc++.h> using namespace std; #define int long long const int maxn = 5e3 + 5; vector<pair<int, int>> adj[maxn]; int sz[maxn], sum[maxn]; int dp[maxn][maxn][2]; void minimize(int &a, int b){ a = min(a, b); } void dfs(int u, int p) { sz[u] = 1; dp[u][1][0] = dp[u][0][0] = 0; dp[u][1][1] = -sum[u]; for (auto [v, w]: adj[u]) { if (v == p) continue; sum[v] = sum[u] + w; 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[u][i + j][0], dp[u][i][0] + dp[v][j][0] + add); minimize(dp[u][i + j][1], min(dp[u][i][0] + dp[v][j][1], dp[u][i][1] + dp[v][j][0]) + add); } } sz[u] += sz[v]; } } void solve(){ int n, k, x; 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}); } memset(dp, 0x3f, sizeof(dp)); dfs(x, 0); cout << dp[x][k][1] << '\n'; } signed main() { ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); solve(); }