## Solución al problema número 11710 de UVA - 11710.

Cualquier duda no dudes en contactar.

#include <bits/stdc++.h>
#define INF 0x3F3F3F3F
using namespace std;

const int MAXN = 200100;

struct edge{
int from, to, weight;
edge(){}
edge(int a, int b, int c){
from = a;
to = b;
weight = c;
}
};

struct state{
int node, dist;
state(){}
state(int a, int b){
node = a; dist = b;
}
bool operator<(const state &other)const{ // sobrecarga de operadores para ordenar
return other.dist < dist;
}
};

vector<edge> graph[MAXN];
bool visited[MAXN];
int dist[MAXN];

int N,E;

int prim(int start){
priority_queue<state> pq;
pq.push(state(start, 0));
dist[start] = 0;
int sum = 0;
while(!pq.empty()){
state cur = pq.top(); pq.pop();
if(dist[cur.node] < cur.dist) continue;
if(visited[cur.node]) continue;
sum += cur.dist;
visited[cur.node] = true;
for(unsigned int i=0;i<graph[cur.node].size();i++){
int dest = graph[cur.node][i].to;
int wht = graph[cur.node][i].weight;
if(visited[dest]) continue;
pq.push(state(dest, wht));
dist[dest] = wht;
}
}
return sum;
}
int main(){
while(scanf("%d %d",&N,&E)==2 && (N!=0||E!=0))
{
memset(visited,0,sizeof(visited));
for(int i=1;i<=N;i++) {dist[i]=INF; graph[i].clear();} // limpia el grafo
map<string,int> M;
for(int i=0; i<N;i++) {string r; cin>>r; M[r]=i+1;}
for(int i=0;i<E;i++){
string a,b; int weight; cin>>a>>b>>weight;
graph[M[a]].push_back(edge(M[a],M[b],weight));
graph[M[b]].push_back(edge(M[b], M[a], weight)); // borrar linea si es dirigido
}
string aux; cin>>aux;
int res = prim(M[aux]);
int flag=1;
for(int i=1; i<=N;i++) if(dist[i]==INF) {flag=0; break;}
if(flag==0) printf("Impossible\n");
else printf("%d\n",res);
}
return 0;
}