#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <climits>#include <string>#include <iostream>#include <map>#include <cstdlib>#include <list>#include <set>#include <queue>#include <stack>using namespace std;typedef long long LL;const int maxn = 105;map<string,int> mp;int maxcost[maxn][maxn],cost[maxn][maxn];int n,cnt,str,ed;string a,b;int id(string &s) {    if(mp.count(s) == 0) mp[s] = ++cnt;    return mp[s];}int main() {    while(cin >> a >> b) {        mp.clear();        cnt = 0;        str = id(a); ed = id(b);        cin >> n;        memset(maxcost,-1,sizeof(maxcost));        memset(cost,-1,sizeof(cost));        for(int i = 1;i <= n;i++) {            int cc;            cin >> a >> b >> cc;            cost[id(a)][id(b)] = cost[id(b)][id(a)] = 0;            maxcost[id(a)][id(b)] = maxcost[id(a)][id(b)] = cc;        }        for(int k = 1;k <= cnt;k++) {            for(int i = 1;i <= cnt;i++) {                for(int j = 1;j <= cnt;j++) if(cost[i][k] != -1 && cost[k][j] != -1) {                    int ca = cost[i][j];                    int cb = cost[i][k] + cost[k][j] + min(maxcost[i][k],maxcost[k][j]);                    if(cb < ca || ca == -1) {                        cost[i][j] = cb;                        maxcost[i][j] = max(maxcost[i][k],maxcost[k][j]);                    }                }            }        }        printf("%d\n",cost[str][ed]);    }    return 0;}