#include <bits/stdc++.h>
using namespace std;
#define int long long
map<int, int> mp, mp2, mp3;
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, k, m;
cin >> n >> k >> m;
int a[n];
for(int i = 0; i < n; i++){
cin >> a[i];
mp3[a[i]]++;
}int cm = m;
while (cm--){
int u, v;
cin >> u >> v;
mp2[u] = v;
}bool ok = false;
for(auto i: mp2){
ok |= (mp3[i.first] < i.second);
}if(ok){
cout << "impossible";
return 0;
}
int l = 0;
int r = 0;
int c = 0;
for(int i = 0; i < n; i++){
mp[a[i]]++;
if(mp2.count(a[i])){
if(mp[a[i]] == mp2[a[i]]){
c++;
}if(c == m){
r = i;
break;
}
}
}int mn = INT_MAX;
while(l < r){
if(mp[a[l]] > mp2[a[l]]){
l++;
mp[a[l]]--;
}else {
break;
}
}mn = min(mn, r-l+1);
for(int i = r+1; i < n; i++){
int num;
while(l < i){
mp[a[l]]--;
if(mp[a[l]] < mp2[a[l]]){
num = a[l];
l++;
break;
}l++;
}while(i < n){
if(mp[num] < mp2[num]){
mp[a[i]]++;
i++;
}else {
break;
}
}mn = min(mn, i-l+1);
}
cout << mn << endl;
}
