#include <iostream>

#include <cstdlib>

#include <cstdio>

#include <algorithm>

#include <vector>

#include <queue>

#include <cmath>

#include <stack>

#include <cstring>

#include <map>

#include <string>

using namespace std;

#define INF 0xfffffff

#define N 12000

#define met(a, b) memset(a, b, sizeof(a))

typedef long long LL;

struct node

{

    int v, t;

    node(int v, int t):v(v), t(t){}

};

vector<vector<node> >G;

int s, e;

int cnt, vis[N], dist[N];

int spfa()

{

    met(vis, );

    for(int i=; i<cnt; i++)

        dist[i] = INF;

    queue<int>Q;

    Q.push(s);

    vis[s] = ;

    dist[s] = ;

    while(Q.size())

    {

        int p = Q.front(); Q.pop();

        vis[p] = ;

        int len = G[p].size(), q;

        for(int i=; i<len; i++)

        {

            q = G[p][i].v;

            if( dist[q] > dist[p]+G[p][i].t )

            {

                dist[q] = dist[p]+G[p][i].t;

                if(vis[q] == )

                {

                    vis[q] = ;

                    Q.push(q);

                }

            }

        }

    }

    return dist[e]==INF?-:dist[e];

}

int main()

{

    int n;

    while(scanf("%d", &n), n!=-)

    {

        map<string, int> M;

        M.clear();

        G.clear();

        G.resize(n*+);

        cnt = ;

        char s1[], s2[];

        scanf("%s %s", s1, s2);

        if( !M[s1] ) M[s1]  = cnt++;

        if( !M[s2] ) M[s2]  = cnt++;

        s = M[s1];

        e = M[s2];

        for(int i=; i<=n; i++)

        {

            int t, u, v;

            scanf("%s %s %d", s1, s2, &t);

            if(!M[s1]) M[s1]  = cnt++;

            if(!M[s2]) M[s2]  = cnt++;

            u = M[s1];

            v = M[s2];

            G[u].push_back(node(v, t));

            G[v].push_back(node(u, t));

        }

        printf("%d\n", spfa());

    }

    return ;

}