#include<iostream>
#include<cstdio>
#include<cstring>
#define N 2009
using namespace std;
long long dp[N][N];
int size[N],m,n,a,b,c,tot,head[N];
struct dsd
{int n,to,l;
}an[N<<1];
inline void add(int u,int v,int l)
{an[++tot].n=head[u];an[tot].to=v;head[u]=tot;an[tot].l=l;
}
void dfs(int u,int fa)
{size[u]=1;for(int i=head[u];i;i=an[i].n)if(an[i].to!=fa){int v=an[i].to;dfs(v,u);size[u]+=size[v];for(int j=min(m,size[u]);j>=0;--j)//
      for(int k=0;k<=min(j,size[v]);++k)if(dp[v][k]!=-0x3f3f3f3f){long long num=(long long)(k*(m-k)+(n-size[v]-(m-k))*(size[v]-k))*an[i].l;dp[u][j]=max(dp[u][j],dp[u][j-k]+dp[v][k]+num);}}
}
int main()
{scanf("%d%d",&n,&m);for(int i=1;i<n;++i){scanf("%d%d%d",&a,&b,&c);add(a,b,c);add(b,a,c);}memset(dp,-0x3f,sizeof(dp));for(int i=1;i<=n;++i)dp[i][0]=dp[i][1]=0;//
    dfs(1,0);cout<<dp[1][m];return 0;
} 

#include<iostream>
#include<cstdio>
#include<cstring>
#define N 2009
using namespace std;
typedef long long ll;
ll dp[N][N],size[N],m,n,a,b,c,tot,head[N],g[N];
struct dsd
{ll n,to,l;
}an[N<<1];
inline void add(ll u,ll v,ll l)
{an[++tot].n=head[u];an[tot].to=v;head[u]=tot;an[tot].l=l;
}
ll mi(ll x,ll y){return x<y?x:y;}
ll ma(ll x,ll y){return x<y?y:x;}
void dfs(ll u,ll fa){size[u]=1;for(ll i=head[u];i;i=an[i].n)if(an[i].to!=fa){ll v=an[i].to;dfs(v,u);ll x=mi(m,size[u]),y=mi(m,size[v]);for(int j=0;j<=m;++j)g[j]=0;for(ll j=x;j>=0;--j)for(int k=0;k<=y;++k)if(j+k<=m){ll gyx=((ll)k*(m-k)+(n-size[v]-(m-k))*(size[v]-k))*an[i].l;g[j+k]=ma(g[j+k],dp[u][j]+dp[v][k]+gyx);}for(int j=0;j<=m;++j)dp[u][j]=g[j];size[u]+=size[v];}
}
inline int rd(){int x=0;char c=getchar();while(!isdigit(c))c=getchar();while(isdigit(c)){x=(x<<1)+(x<<3)+(c^48);c=getchar();}return x;
}
int main()
{n=rd();m=rd();for(int i=1;i<n;++i){a=rd();b=rd();c=rd();add(a,b,c);add(b,a,c);}memset(dp,-0x3f,sizeof(dp));for(int i=1;i<=n;++i)dp[i][0]=dp[i][1]=0;dfs(1,0);printf("%lld",dp[1][m]);return 0;
}