#include <bits/stdc++.h>

 using namespace std;

 typedef pair<int, int> pii;

 const int MAXN = ;

 vector<pii> G[MAXN];

 int dp[MAXN][], n, s, k;

 void dfs(int u, int f)

 {

     for (int i = ; i < G[u].size(); i++)

     {

         int v = G[u][i].first, w = G[u][i].second;

         if (v == f) continue;

         dfs(v, u);

         for (int j = k; j >= ; j--)

         {

             dp[u][j] += dp[v][] +  * w;

             for (int l = ; l <= j; l++)

             {

                 dp[u][j] = min(dp[u][j], dp[v][l] + l * w + dp[u][j - l]);

             }

         }

     }

 }

 int main()

 {

     while (scanf("%d %d %d", &n, &s, &k) != EOF)

     {

         memset(dp, , sizeof dp);

         for (int i = ; i <= n; i++) G[i].clear();

         int a, b, w;

         for (int i = ; i < n - ; i++)

         {

             scanf("%d %d %d", &a, &b, &w);

             G[a].push_back(pii(b, w));

             G[b].push_back(pii(a, w));

         }

         dfs(s, );

         printf("%d\n", dp[s][k]);

     }

     return ;

 }