#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, k, r; cin >> n >> k >> r;
vector<int> freq(k, 1e18);
vector<int> x(n);
for(int i = 0; i < n; i++){
cin >> x[i];
}
for(int i = 0; i < r; i++){
int a, f; cin >> a >> f;
freq[a] = f;
}
int co = 0;
int it = 0;
vector<int> f(k);
for(int i = 0; i < n; i++){
f[x[i]]++;
if(f[x[i]] == freq[x[i]]){
co++;
}
if(co == r){
it = i+1;
break;
}
}
if(it == 0){
cout << "impossible" << "\n";
return 0;
}
int ns = it;
int i = it;
int size = ns;
int l = 0;
while(l < it-1){
if(f[x[l]] != freq[x[l]]){
f[x[l]]--;
l++;
}else{
break;
}
}
ns = min(ns, it - l);
for(int i = it; i < n; i++){
f[x[i]]++;
while(l < i){
if(f[x[l]] != freq[x[l]]){
f[x[l]]--;
l++;
}else{
break;
}
}
ns = min(ns, i - l + 1);
}
cout << ns << "\n";
return 0;
}
