#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define MAXN (1000005)
int main() {
ios_base::sync_with_stdio(false);cin.tie(0);
ll N,K,R;
cin>>N>>K>>R;
ll arr[N];
for(ll i = 0;i < N;i++){
cin>>arr[i];
}
ll cnt[K];
memset(cnt,0,sizeof(cnt));
ll atleast[K];
memset(atleast,0,sizeof(atleast));
set<pair<ll,ll> > shortage;
for(ll i = 0;i < R;i++){
ll b,q;
cin>>b>>q;
atleast[b] = q;
shortage.insert({q,b});
}
ll minimum = 1e18;
ll l = 0;
for(ll r = 0;r < N;r++){
if(cnt[arr[r]] < atleast[arr[r]]){
auto it = shortage.find({atleast[arr[r]] - cnt[arr[r]],arr[r]});
shortage.erase(it);
cnt[arr[r]]++;
if(cnt[arr[r]] < atleast[arr[r]]){
shortage.insert({atleast[arr[r]] - cnt[arr[r]],arr[r]});
}
}else{
cnt[arr[r]]++;
}
if(shortage.empty()){
while(l < r && cnt[arr[l]] > atleast[arr[l]]){
cnt[arr[l]]--;
l++;
}
minimum = min(minimum,r - l + 1);
}
}
if(!shortage.empty()) cout<<"impossible"<<'\n';
else cout<<minimum<<'\n';
}
