#include<bits/stdc++.h>
using namespace std;

typedef struct lnod {
    int nod;
    lnod *next;
}*nod;

int i,j,d,n,x,y,m,dp[1005];
bool a[1005];
nod lda[1005];

void add(int x,nod &y) {
    nod p=new lnod;
    p->nod=x;
    p->next=y;
    y=p;
}

int main()
{
  ios_base::sync_with_stdio(0); cin.tie(0);

  cin>>d>>n>>m;
  for(i=1;i<=n;++i) cin>>x,a[x]=1;
  for(i=1;i<=m;++i) cin>>x>>y,add(y,lda[x]);

  for(i=1;i<=d;++i) dp[i]=2e9+69;

  for(i=0;i<=d;++i)
  {
    if(!a[i+1]) dp[i+1]=min(dp[i+1],dp[i]);
    for(nod p=lda[i+1];p;p=p->next)
    dp[p->nod]=min(dp[p->nod],dp[i]+1);
  }

  cout<<dp[d]<<'\n';

 return 0;
}