#include <map>

#include <set>

#include <list>

#include <cmath>

#include <queue>

#include <stack>

#include <cstdio>

#include <vector>

#include <string>

#include <cctype>

#include <complex>

#include <cassert>

#include <utility>

#include <cstring>

#include <cstdlib>

#include <iostream>

#include <algorithm>

using namespace std;

typedef pair<int,int> PII;

typedef long long ll;

#define lson l,m,rt<<1

#define pi acos(-1.0)

#define rson m+1,r,rt<<11

#define All 1,N,1

#define read freopen("in.txt", "r", stdin)

const ll  INFll = 0x3f3f3f3f3f3f3f3fLL;

const int INF= 0x7ffffff;

const int mod =  ;

struct tree{

    int u,v,next,cost;

}t[];

int dp[][],n,k,s,used[],head[],len;

void add(int a,int b,int c){

    t[len].u=a;

    t[len].v=b;

    t[len].cost=c;

    t[len].next=head[a];

    head[a]=len++;

}

void dfs(int root){

    used[root]=;

    for(int i=head[root];i!=-;i=t[i].next){

        int son=t[i].v;

        if(used[son])continue;

        dfs(son);

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

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

            dp[root][j]=max(dp[root][j],dp[root][j-l]+dp[son][l]+(-l)*t[i].cost);//l个机器人过这个边，减少的花费(2-l)*t[i].cost

    }

}

int main()

{

    while(~scanf("%d%d%d",&n,&s,&k)){

            memset(dp,,sizeof(dp));

            memset(used,,sizeof(used));

            memset(head,-,sizeof(head));

        int a,b,c,sum=;

        len=;

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

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

            sum+=c;

            add(a,b,c);

            add(b,a,c);

        }

        dfs(s);

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

    }

return ;

}