/*hdu 3592的原题少了一个输入控制。。。
hdu的题解我有些详解的*/
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
using namespace std;
const int INF = 1<<26;
struct node{
int y,w,next;
}edge[150005];
int dis[10010],n,m1,edgeHead[10010],stack[100010],m2,cot[10010];
bool vis[10010];
bool spfa(){//下表为1开始
for(int i = 2; i <= n; i ++)
{
dis[i] = INF;
cot[i] = 0;
}
dis[1] = 0;
int top = 0;     //  spfa的堆栈实现模板。
stack[++ top] = 1;
vis[1] = true;
while(top){
int x = stack[top --];
cot[x]++;
if(cot[x]>n) return false;
for(int p = edgeHead[x]; p != 0; p = edge[p].next){
int y = edge[p].y;
if(dis[y] > dis[x] + edge[p].w){
dis[y] = dis[x] + edge[p].w;
if(!vis[y]){
vis[y] = true;
stack[++ top] = y;
}
}
}
vis[x] = false;
}
return true;
}
int main()
{
int i,j,t;
int x,y,v,k=1;
while(scanf("%d %d %d",&n,&m1,&m2)!=EOF)
{
for(i=1;i<=n;i++)
{
edge[i].next=0;
edgeHead[i]=0;
}
for(i=1;i<=m1;i++)//d[y]-d[x]<=c
{
scanf("%d %d %d",&x,&y,&v);
edge[k].y=y;
edge[k].w=v;
edge[k].next=edgeHead[x];
edgeHead[x]=k++;
}
for(i=1;i<=m2;i++)//d[y]-d[x]>=c  =>  d[x]-d[y]<=-c
{
scanf("%d %d %d",&x,&y,&v);
edge[k].y=x;
edge[k].w=-v;
edge[k].next=edgeHead[y];
edgeHead[y]=k++;
}
for(i=1;i<=n;i++)
{
edge[k].y=i;
edge[k].w=0;
edge[k].next=edgeHead[i+1];
edgeHead[i+1]=k++;
}
int ans;
if(!spfa()) ans = -1;
else if(dis[n] == INF) ans = -2;
else ans=dis[n];
printf("%d\n",ans);
}
return 0;
}