#include <cstdio>
#include <iostream>
#include <sstream>
#include <vector>
//MYDELKO TYM!!!
using namespace std;
int delka = 0;
vector <int> maslo;
int rekurzivni(int pole[][3], int x,int node)
{
bool nalezeno = false;
for(int i=0;i<node-1;i++){
cout << "A" << endl;
if(pole[i][0] == x)
{
cout << "B" << endl;
if(rekurzivni(pole, pole[i][1], node) == 1)
{
cout << "C" << endl;
delka = pole[i][2];
cout << "D" << endl;
}
}
if(pole[i][1] == x)
{
cout << "B" << endl;
if(rekurzivni(pole, pole[i][1], node) == 1)
{
cout << "C" << endl;
delka = pole[i][2];
cout << "D" << endl;
}
}
}
cout << "F" << endl;
if (nalezeno == false)
{
return 1;
}
else return 0;
}
int main(){
string test;
int node=0;
int central;
while(cin >> node >> central){
delka = 0;
int pole[node][3];
for(int i=0;i<node-1;i++){
cin >> pole[i][0];
cin >> pole[i][1];
cin >> pole[i][2];
}
/*
for(int i=0;i<node-1;i++){
cout << pole[i][0] << pole[i][1] << pole[i][2] << endl;
}
*/
int pole_pocitadlo[node+5];
for(int i =0;i<node+1;i++){
pole_pocitadlo[i]=0;
}
for(int i =0;i<node-1;i++){
pole_pocitadlo[pole[i][0]] ++;
pole_pocitadlo[pole[i][1]] ++;
}
/*
for(int i =0;i<node+1;i++){
cout << i <<" " << pole_pocitadlo[i] << endl;
}
*/
for(int i =0;i<node-1;i++){
if(pole_pocitadlo[pole[i][0]] == 1 || pole_pocitadlo[pole[i][1]] == 1 ) delka += pole[i][2];
}
/*
for(int i=0;i<node-1;i++){
for(int q=0;q<node-1;q++){
if(pole[i][0] != pole[q][0])
delka += pole[q][2];
else if(pole[i][0] != pole[q][1])
delka += pole[q][2];
else if(pole[i][1] != pole[q][0])
delka += pole[q][2];
else if(pole[i][1] != pole[q][1])
delka += pole[q][2];
}
}
*/
cout << delka << endl;
}
return 0;
}