#include <bits/stdc++.h>
using namespace std;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
long long n,k,r;cin >> n >> k >> r;
vector<long long> v(n);
set<long long> s;
map<long long,long long> m;
long long check[n];
for(int i = 0;i<n;i++){
cin >> v[i];
}
for(int i = 0;i<r;i++){
long long gene,required;
cin >> gene >> required;
m[gene] = required;
}
long long left = 0;
long long current = 0;
long long ans = LLONG_MAX;
long long completed = 0;
map<long long, long long> track;
for(int i = 0;i<n;i++){
if (track[v[i]] == 0){
track[v[i]] = 1;
}
else{
track[v[i]] += 1;
}
if (m.find(v[i]) != m.end() && track[v[i]] >= m[v[i]] && check[v[i]] == 0){
completed += 1;
check[v[i]] = 1;
}
while (completed >= r){
ans = min(ans,i - left+ 1);
track[v[left]]--;
if (m.find(v[left]) != m.end() && track[v[left]] <m[v[left]] && check[v[left]] == 1){
completed--;
check[v[left]] = 0;
}
left++;
}
}
if (ans == LLONG_MAX){
cout << "impossible";
return 0;
}
cout << ans;
}
