#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<cstdlib>

 #include<queue>

 using namespace std;

 #define INF  0x3f3f3f3f

 #define maxn 1010

 int dis[maxn];

 int path[maxn];

 int inq[maxn];

 int cnt[maxn];

 class node

 {

     public:

     int to;

     int w;

     int next;

 };

 node edge[maxn*];

 int head[maxn*];

 int tol;

 int n,ML,MD;

 void add(int u,int v,int w)

 {

    edge[tol].to=v;

    edge[tol].w =w;

    edge[tol].next=head[u];

    head[u]=tol++;

 };

 queue<int>Q;

 bool SPFA()

 {

       memset(inq,,sizeof(inq));

       memset(cnt,,sizeof(cnt));

       int v0=;

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

      {

          dis[i]=INF;

          path[i]=v0;

          inq[i]=;

      }

      dis[v0]=;

      path[v0]=v0;

      inq[v0]++;

      cnt[v0]++;

      Q.push(v0);

      while(!Q.empty())

      {

           int u=Q.front();

           Q.pop();

           inq[u]--;

           int tmp=head[u];

           while(tmp!=-)

           {

               int v=edge[tmp].to;

               int w=edge[tmp].w;

               if(dis[v]>dis[u]+w)

               {

                   dis[v]=dis[u]+w;

                   path[v]=u;

                   if(inq[v]==)

                   {

                      inq[v]++;

                      if(++cnt[v]>n) return false;

                      Q.push(v);

                   }

               }

               tmp=edge[tmp].next;

           }

      }

      return true;

 }

 int main()

 {

    int a,b,d;

   while(scanf("%d%d%d",&n,&ML,&MD)!=EOF)

   {

       tol=;

       memset(head,-,sizeof(head));

       while(ML--)

       {

            scanf("%d%d%d",&a,&b,&d);

            add(a,b,d);

       }

       while(MD--)

       {

           scanf("%d%d%d",&a,&b,&d);

           add(b,a,-d);

       }

       if(!SPFA()) cout<<"-1"<<endl;

        else

          if(dis[n]>=INF) cout<<"-2"<<endl;

             else cout<<dis[n]<<endl;

   }

   return ;

 }