//
//  main.cpp
//  hdu4003
//
//  Created by Candy on 9/23/16.
//  Copyright © 2016 Candy. All rights reserved.
//

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
const int N=1e4+5,M=12;
int read(){
    char c=getchar();int x=0,f=1;
    while(c<‘0‘||c>‘9‘){if(c==‘-‘)f=-1; c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){x=x*10+c-‘0‘; c=getchar();}
    return x*f;
}
struct edge{
    int v,w,ne;
}e[N<<1];
int h[N],cnt=0;
void ins(int u,int v,int w){
    cnt++;
    e[cnt].v=v;e[cnt].w=w;e[cnt].ne=h[u];h[u]=cnt;
    cnt++;
    e[cnt].v=u;e[cnt].w=w;e[cnt].ne=h[v];h[v]=cnt;
}
int  n,s,m,u,v,w;
int f[N][M];
void dp(int u,int fa){
    for(int i=h[u];i;i=e[i].ne){
        int v=e[i].v,w=e[i].w;
        if(v==fa) continue;
        dp(v,u);
        for(int j=m;j>=0;j--){  //ti ji
            f[u][j]+=f[v][0]+w*2;//must choose
            for(int k=1;k<=j;k++)//group
                f[u][j]=min(f[u][j],f[u][j-k]+f[v][k]+w*k);
        }
    }
}
int main(int argc, const char * argv[]) {
    while(cin>>n>>s>>m){
        cnt=0;
        memset(h,0,sizeof(h));
        for(int i=1;i<=n-1;i++){
            u=read();v=read();w=read();
            ins(u,v,w);
        }
        memset(f,0,sizeof(f));
        dp(s,0);
        printf("%d\n",f[s][m]);
    }
    return 0;
}