#include<iostream>
#include<fstream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<string>
#include<queue>
#include<cstdlib>
#include<ctime>
#include<map>
#define in cin
#define out cout
#define FOR(i, a, b) for(int i = a; i <= b; ++i)
using namespace std;
typedef long long ll;
const int INF = 0x3f3f3f3f;
const int Nmax = 2001;
vector<int> G[Nmax];
int a[Nmax],m[Nmax],s[Nmax];
int d[Nmax];
int main(){
    #ifndef ONLINE_JUDGE
    ifstream in("test.in");
    ofstream out("test.out");
    #endif
    int N,M,D; in>>D>>N>>M;
    FOR(i,1,N) in>>a[i],m[a[i]]=1;
    FOR(i,1,D) s[i]=s[i-1]+m[i];
    sort(a+1,a+N+1);
    FOR(i,1,M){
        int x,y;
        in>>x>>y;
        if(s[y]-s[x-1]>0) G[x].push_back(y);
    }
    for(int i=1;i<=D;i++) d[i]=INF;
    int cur=0;
    for(int i=1;i<=D;i++){
        cur=min(cur,d[i]);
        for(vector<int>::iterator it=G[i].begin();it!=G[i].end();++it){
            d[*it]=min(d[*it],cur+1);
        }
        if(m[i]) cur=d[i];
    }
    out<<cur<<'\n';
    return 0;
}