/*
Author: 2486
Memory: 2136 KB     Time: 3151 MS
Language: G++     Result: Accepted
*/
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <map>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <cstdlib>
using namespace std;
const int maxn=170;
const int INF=100000000;
map<string,int>F;
string st,en,n1,n2;
int val,cnt,n;
struct edge {int to,cost;edge(int to,int cost):to(to),cost(cost) {}
};
vector<edge>G[maxn];
int d[maxn];
typedef pair<int,int>P;
void init() {for(int i=0; i<maxn; i++)G[i].clear();F.clear();
}
void dijkstra(int s) {priority_queue<P,vector<P>,greater<P> >que;for(int i=0;i<cnt;i++)d[i]=INF;d[s]=0;que.push(P(0,s));while(!que.empty()) {P p=que.top();que.pop();int  v=p.second;if(d[v]<p.first)continue;for(int i=0; i<G[v].size(); i++) {edge e=G[v][i];if(d[e.to]>d[v]+e.cost) {d[e.to]=d[v]+e.cost;que.push(P(d[e.to],e.to));}}}
}
int main() {//freopen("D://imput.txt","r",stdin);while(~scanf("%d",&n),n!=-1) {cnt=1;init();cin>>st>>en;F[st]=cnt++;F[en]=cnt++;for(int i=0; i<n; i++) {cin>>n1>>n2>>val;if(F[n1]==0)F[n1]=cnt++;if(F[n2]==0)F[n2]=cnt++;G[F[n1]].push_back(edge(F[n2],val));G[F[n2]].push_back(edge(F[n1],val));}dijkstra(F[st]);if(d[F[en]]==INF)printf("-1\n");elseprintf("%d\n",d[F[en]]);}return 0;
}

int dis[155];
bool vis[155];
void dijkstra(int start,int thend) {for(int i=0; i<155; i++)dis[i]=INF,vis[i]=0;dis[start]=0,vis[start]=1;queue<int>q;q.push(start);while(!q.empty()) {int u=q.front();q.pop();vis[u]=0;for(int j=0; j<g[u].size(); j++) {int v=g[u][j].v;int t=g[u][j].t;if(dis[v]>dis[u]+t) {dis[v]=dis[u]+t;if(!vis[v]) {vis[v]=1;q.push(v);}}}}if(dis[thend]>=INF)puts("-1");elseprintf("%d\n",dis[thend]);
}