#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e9+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ll,ii>
#define id pair<ll,vector<ll> >
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
int main(void){
ll n,k,r;
cin>>n>>k>>r;
ll arr[n];
ll re[k] = {0};
f(i,0,n){
cin>>arr[i];
}
vector<ll>ex[k];
f(i,0,n){
ex[arr[i]].pb(i);
}
f(i,0,k){
reverse(all(ex[i]));
}
f(i,0,r){
ll b,q;
cin>>b>>q;
re[b] = max(re[b],q);
}
ll len = 0;
f(i,0,k){
if(ex[i].size() < re[i]){
cout<<"impossible\n";
return 0;
}
if(re[i]){
len = max(len,ex[i][ex[i].size() - re[i]]);
}
}
ll ans = len+1;
f(i,0,n){
ex[arr[i]].pop_back();
if(ex[arr[i]].size() < re[arr[i]]){
break;
}
if(re[arr[i]])
len = max(len,ex[arr[i]][ex[arr[i]].size() - re[arr[i]]]);
ans = min(ans,len - i);
}
cout<<ans<<"\n";
}
