#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;

struct State
{
    int price, to;
    State( int p, int t ) : price(p), to(t) {}
    bool operator<( const State& s ) const
    {
        if( price == s.price )  return to < s.to;
        return price > s.price;
    }
};

int N, M, K;
vector <State> v[10000];

void input()
{
    scanf("%d %d %d", &N, &M, &K);

    int x, y;
    for( int i = 0; i < M; i++ )
    {
        scanf("%d %d", &x, &y);
        v[x].push_back(State(0, y));
        v[y].push_back(State(0, x));
    }

    for( int i = 0; i < K; i++ )
    {
        scanf("%d %d", &x, &y);
        v[x].push_back(State(1, y));
        v[y].push_back(State(1, x));
    }
}

int dist[10000];
void dijkstra( int start )
{
    bool used[10000] = {0};
    used[start] = 1;

    priority_queue <State> pq;
    memset(dist, 63, sizeof(dist));
    for( int i = 0; i < v[start].size(); i++ )
    {
        dist[v[start][i].to] = v[start][i].price;
        pq.push(v[start][i]);
    }

    while( !pq.empty() )
    {
        int vertex = pq.top().to;
        pq.pop();

        if( used[vertex] )  continue;
        used[vertex] = 1;

        for( int i = 0; i < v[vertex].size(); i++ )
            if( !used[v[vertex][i].to] && dist[vertex] + v[vertex][i].price < dist[v[vertex][i].to] )
            {
                dist[v[vertex][i].to] = dist[vertex] + v[vertex][i].price;
                pq.push(State(dist[v[vertex][i].to], v[vertex][i].to));
            }
    }
}


int main()
{
    input();
    dijkstra(N-1);

    int ans = dist[0];
    if( dist[0] >= N )
    ans = 0;

    if( ans == 0 )  printf("-1\n");
    else            printf("%d\n", ans);

    return 0;
}