fr.cpp

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <utility>
#include <string>
#include <deque>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
using namespace std;
 
#define debug printf
//#define debug blackhole
void blackhole(...) {}
 
int ADJACENT[2000][2000];
int ADJACENT_W[2000][2000];
int ADJ_N[2000];
int V;
 
long RECURSE(long FROM_W, long FROM_V, int v) {
	long ss = 0;
	if (ADJ_N[v] == 1) return FROM_W;
	for (int i = 0; i < ADJ_N[v]; i++) {
		if (ADJACENT[v][i] == FROM_V) continue;
		ss += RECURSE(ADJACENT_W[v][i], v, ADJACENT[v][i]);
		if (FROM_W != -1 && FROM_W < ss) {
			ss = FROM_W; break;
		}
	}
	if (FROM_W != -1 && FROM_W < ss) ss = FROM_W;
	return ss;
}
 
void GO(int KOR) {
	for (int i=0;i<V;i++) {
		ADJ_N[i]=0;
	}
	for (int i = 0; i < V - 1; i++) {
		int a, b, weight;
		scanf("%d%d%d", &a, &b, &weight);
		ADJACENT[a][ADJ_N[a]] = b;
		ADJACENT_W[a][ADJ_N[a]++] = weight;
		ADJACENT[b][ADJ_N[b]] = a;
		ADJACENT_W[b][ADJ_N[b]++] = weight;
	}
 
	printf("%ld\n", RECURSE(-1, -1, KOR));
}
 
int main() {
	while (true) {
		int KOR;
		if (scanf("%d%d", &V, &KOR) != 2) break;
		GO(KOR);
	}
	return 0;
}