#include <bits/stdc++.h>
#define inf 0x3f3f3f3f
#define met(a,b) memset(a,b,sizeof a)
#define pb push_back
#define mp make_pair
#define rep(i,l,r) for(int i=(l);i<=(r);++i)
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
const int N = 1e6+50;;
const int M = 255;
const int mod = 19260817;
const int mo=123;
const double pi= acos(-1.0);
typedef pair<int,int>pii;
int n,k,cas;
ll ans;
int sz[N];
vector<pii>edg[N];
void dfs(int u,int fa){
    sz[u]=1;
    for(auto e : edg[u]){
        int v=e.first;
        int w=e.second;
        if(v==fa)continue;
        dfs(v,u);
        sz[u]+=sz[v];
        ans+=1LL*w*min(sz[v],k);
    }
}
int main(){
    //int T;
    //scanf("%d",&T);
    while(~scanf("%d%d",&n,&k)){
        for(int i=1;i<=n;i++)edg[i].clear();
        for(int i=1,u,v,w;i<n;i++){
            scanf("%d%d%d",&u,&v,&w);
            edg[u].pb(mp(v,w));edg[v].pb(mp(u,w));
        }
        ans=0;
        dfs(1,0);
        printf("%lld\n",ans);
    }
    return 0;
}