fr.cpp

#include <cstdio>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits.h>
#include <map>
#include <queue>
#include <vector>
#include <set>
#include <stack>
#include <bitset>
#include <string>
 
using namespace std;
 
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef set<int> si;
typedef set<ii> sii;
 
#define MP make_pair
#define PB push_back
#define REP(i,a) for ( int i = 0; i < int(a); i++)
#define FOR(i,a,b) for ( int i = int(a); i<=int(b); i++)
#define FORD(i,a,b) for(int i= int(a); i>=int(b); i--)
 
const int INF = 1<<29;
typedef long long int ll;
 
struct node
{
	bool visited;
	int  parent;
	vii  adj;
} nodes[1001];
 
int dfs( int v, int cap )
{
	//printf("node%d %d\n", v, cap);
	nodes[v].visited = true;
	int sum = 0;
	FOR( i, 0, nodes[v].adj.size( )-1 )
	{
		if ( !nodes[ nodes[v].adj[i].first ].visited )
			sum += dfs( nodes[v].adj[i].first, nodes[v].adj[i].second );
	}
	if ( sum == 0 )
		return cap;
	return sum;
}
 
int main()
{
	int n, c, u, v, w;
	while ( scanf("%d%d", &n, &c) == 2 )
	{
		FOR( i, 1, n )
		{
			nodes[i].parent  = 0;
			nodes[i].visited = false;
			nodes[i].adj.clear( );
		}
		FOR( i, 1, n-1 )
		{
			scanf("%d%d%d", &u, &v, &w);
			nodes[u].adj.PB( MP( v, w ) );
			nodes[v].adj.PB( MP( u, w ) );
		}
		printf("%d\n", dfs( c, INT_MAX ));
	}
  return 0;
}