#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("a.in");
ofstream fout("a.out");
#define MAX 1004
#define fin cin
int ok[MAX], rez[MAX];
pair<int, int> a[MAX];

int main()
{
    int d, n, m, i, x, j;
    fin >> d >> n >> m;
    for(i = 1 ; i <= n ; i++)
    {
        fin >> x;
        ok[x] = 1;
       // cout << x << " ";
    }
    for(i = 1 ; i <= m ; i++)
        fin >> a[i].first >> a[i].second;
    for(i = 1 ; i <= d ; i++)
    {
        rez[i] = 100000;
        if(!ok[i])
            rez[i] = rez[i - 1];
        for(j = 1 ; j <= m ; j++)
        {

            if(a[j].second == i && a[j].first <= i)
            {
                rez[i] = min(rez[i], rez[a[j].first - 1] + 1);
                //cout << j << " " << rez[i] << "\n";
            }
        }

    }
    cout << rez[d] << "\n";
}