#include <cstring>
#include <iostream>
#include <vector>

using namespace std;

const int LEN = 1005;

int D, N, M;
bool a[LEN];

vector<int> l[LEN];
int d[LEN];

int main() {
   memset(d, 0x3f, sizeof d);
   cin >> D >> N >> M;

   while (N--) {
      int x;
      cin >> x;
      a[x] = true;
   }

   while (M--) {
      int x, y;
      cin >> x >> y;
      l[x].push_back(y + 1);
   }

   d[D + 1] = 0;
   for (int i = D; i > 0; --i) {
      if (!a[i])
         d[i] = min(d[i], d[i + 1]);
      for (int j : l[i])
         d[i] = min(d[i], d[j] + 1);
   }

   cout << d[1] << "\n";
   return 0;
}