#include? < stdio.h >
#include? < stdlib.h >
#include? < string .h >

#define ?N?1005
#define ?inf?1<<29

struct ?Edge{
???? int ?u,?v,?d;
????Edge(? int ?a = ? 0 ,? int ?b = ? 0 ,? int ?c = ? 0 ?):
????????u(a),?v(b),?d(c)?{}
};

int ?n,?ml,?md,?s = ? 0 ;
Edge??ege[ 20010 ];
int ?dist[N];

int ?bell_man(){
???? for (? int ?i = ? 1 ;?i <= ?n;? ++ i?)?dist[i] = ?inf;
????dist[ 1 ] = ? 0 ;
????
???? int ?flag = ? 0 ;
???? for (? int ?i = ? 1 ;?i <= ?n;? ++ i?){
????????flag = ? 0 ;
???????? for (? int ?j = ? 0 ;?j < ?s;? ++ j?){
???????????? int ?u = ?ege[j].u,?v = ?ege[j].v,?w = ?ege[j].d;
???????????? if (?dist[u] + ?w < ?dist[v]?)?dist[v] = ?dist[u] + ?w,?flag = ? 1 ;
????????}
???????? if (? ! flag?)? break ;
????}
???? if (?flag?)? return ? - 1 ;
???? else ? if (?dist[n] == ?inf?)? return ? - 2 ;
???? else ? return ?dist[n];
}

int ?main(){
????scanf( " %d%d%d " , & n, & ml, & md?);
???? int ?u,?v,?d;
???? while (?ml -- ?){
????????scanf( " %d%d%d " , & u, & v, & d?);
????????ege[s ++ ] = ?Edge(?u,?v,?d?);
????}
???? while (?md -- ?){
????????scanf( " %d%d%d " , & u, & v, & d?);
????????ege[s ++ ] = ?Edge(?v,?u,? - d?);
????}
????printf( " %d\n " ,?bell_man()?);

???? return ? 0 ;
}