#include <cstdio>
#include <algorithm>
#include <vector>
#include <cstring>

using namespace std;

int din[1024];
bool ap[1024];
vector <int> v[1024];

int main()
{
   // freopen ("file.in", "r", stdin);

    int d, n, m;
    scanf ("%d %d %d", &d, &n, &m);

    for (; n; --n)
    {
        int x;
        scanf ("%d", &x);

        ap[x] = true;
    }

    for (; m; --m)
    {
        int a, b;
        scanf ("%d %d", &a, &b);

        v[a].push_back (b);
    }

    memset (din, 0x77777777, sizeof (din));

    din[d + 1] = 0;

    for (; d; --d)
    {
        if (!ap[d]) din[d] = min (din[d], din[d + 1]);

        for (int i = 0; i < v[d].size (); ++i)
            din[d] = min (din[d], din[v[d][i] + 1] + 1);
    }

    printf ("%d\n", din[1]);

    return 0;
}