http://acm.hdu.edu.cn/showproblem.php?pid=6060
#include<bits/stdc++.h>
using namespace std;
#define ll long long
const ll MAXN=1e6+10;
ll n,k;
struct Edge
{
ll to,cost;
Edge(){}
Edge(ll a,ll b):to(a),cost(b){}
};
vector<Edge>G[MAXN];
ll son[MAXN];
ll ans=0;
void init()
{
ans=0;
for(ll i=0;i<MAXN;i++)
{
G[i].clear();
}
memset(son,0,sizeof(son));
}
void dfs(ll u,ll fa)
{
son[u]++;
for(ll i=0;i<G[u].size();i++)
{
Edge e=G[u][i];
if(e.to==fa)continue;
dfs(e.to,u);
son[u]+=son[e.to];
ans+=min(son[e.to],k)*e.cost;
}
}
void solve()
{
dfs(1,-1);
printf("%lld\n",ans);
}
int main()
{
while(scanf("%lld%lld",&n,&k)!=EOF)
{
init();
ll a,b,c;
for(ll i=0;i<n-1;i++)
{
scanf("%lld%lld%lld",&a,&b,&c);
G[a].push_back(Edge(b,c));
G[b].push_back(Edge(a,c));
}
solve();
}
return 0;
}