#include<bits/stdc++.h>
#define endl "\n"
using namespace std ;
typedef long long ll;
typedef long double ld ;
#define pb push_back
#define pp pop_back
const int N=1e6+9;
const ll inf=1e18 ;
const ll mod = 1e9+9 ;
#define fast ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
ll n,k,q,cnt[N],freq[N],x,y,a[N],l,r;
map<ll,ll>mp1;
map<ll,ll>mp;
bool b=0;
int main()
{
fast;
ll ans=inf;
cin>>n>>k>>q;
for(int i=0; i<n; i++){
cin>>a[i];
}
while(q--){
cin>>x>>y;
mp1[x]+=y;
}
for(ll i=0; i<n; i++){
mp[a[i]]++;
b=1;
for(auto i:mp1){
if(mp[i.first]>=i.second){
b=1;
}
else{
b=0;
break;
}
}
while(mp[a[l]]>mp1[a[l]]) {
mp[a[l]]--;
l++;
}
if(b)ans=min(ans,i-l);
}
if(ans==inf)cout<<"impossible";
else cout<<ans+1;
return 0;
}
