#include<cstdio>
#include<bitset>
#include<vector>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<ctime>
#include<map>
#include<set>
#include<queue>
#include<algorithm>

using namespace std;

int INF = 10000, D, M, N, dp[1009], ap[1009];
vector < int > v[1009];

int main()
{
//sfreopen ("input", "r", stdin);
//freopen ("output", "w", stdout);

scanf ("%d %d %d", &D, &N, &M);
for (int i=1; i<=N; i++)
{
    int x;
    scanf ("%d", &x), ap[x] = 1;
}
for (int i=1; i<=M; i++)
{
    int x, y;
    scanf ("%d %d", &x, &y);
    v[y].push_back (x - 1);
}
dp[0] = 0;
for (int i=1; i<=D; i++)
{
    if (ap[i] == 0)
    {
        dp[i] = dp[i - 1];
        for (vector < int > :: iterator it = v[i].begin (); it != v[i].end (); it ++)
            if (dp[*it] + 1 < dp[i]) dp[i] = dp[*it] + 1;
    }
    else
    {
        dp[i] = INF;
        for (vector < int > :: iterator it = v[i].begin (); it != v[i].end (); it ++)
            if (dp[*it] < dp[i]) dp[i] = dp[*it];
        dp[i] ++;
    }
}
printf ("%d\n", dp[D]);
return 0;
}