#include <bits/stdc++.h> 
using namespace std;
#define ll long long
const int N = 1e5+10;
const ll mod = 998244353;

ll read(){
    ll x = 0,f = 1;char c = getchar();
    for(;c < '0' || c > '9';c = getchar())if(c == '-')f = -1;
    for(;c >= '0' && c <= '9';c = getchar())x = (x<<1) + (x<<3) + c-'0';
    return x * f;
}

struct made{
    int ver,nx;ll ed;
}e[N<<1];
int hd[N],tot;
void link(int x,int y,ll z){e[++tot] = {y,hd[x],z},hd[x] = tot;}

int n,m;



ll s = 0,d[N];
void dp(int x,int fa){
    for(int i = hd[x];i;i = e[i].nx){
        int y = e[i].ver;ll z = e[i].ed;
        if(y == fa)continue;
        dp(y,x);//先遍历儿子 
        s = max(s,d[x] + d[y] + z);
        d[x] = max(d[x],d[y] + z);
    }
}
solve1(){
    dp(1,0);
    printf("%lld\n",s);
}

int main(){
    freopen("2018track.in","r",stdin);
    freopen("2018track.out","w",stdout);
    n = read(),m = read();
    for(int i = 1;i < n;i++){
        int x = read(),y = read();ll z = read();
        link(x,y,z),link(y,x,z);
    }
    if(m == 1)solve1();

    
    return 0;
    
}