#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef vector<int>vi;
#define pb push_back
#define sz(v) (int)v.size()
#define FOR(i,a,b) for(int i=a; i<b; i++)
void IO(){
#ifdef LOCAL
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
#endif
}
//------------------------------------------------------//
void ckmin(int &x, int y){x=min(x,y);}
const int MX=2e5;
int N,K,R;
vi a(MX),rq(MX,0);
int main(){
IO();
cin>>N>>K>>R;
FOR(i,0,N) cin>>a[i];
FOR(i,0,R){
int x; cin>>x;
cin>>rq[x];
}
int j=0,needed=R,ans=1e9;
vi cnt(K,0);
FOR(i,0,N){
cnt[a[i]]++;
if(cnt[a[i]]==rq[a[i]]) needed--;
if(needed==0){
while(cnt[a[j]]-1>=rq[a[j]]){
cnt[a[j]]--;
j++;
}
ckmin(ans,i-j+1);
}
}
if(ans==1e9) cout << "impossible" << endl;
else cout << ans << endl;
}
