#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define int long long
#define all(a) a.begin(),a.end()
#define pb push_back
const int mod = 1e9 + 7;
const int maxn = 2e5 + 5;
const int lg = 30 ;
void solve(){
int n,k,q;
cin>>n>>k>>q;
vector <int> a(n);
for(int& i : a)cin>>i;
vector <int> nm(maxn, 0);
while(q--){
int b,c;
cin>>b>>c;
nm[b] = c;
}
vector <vector <int>> pre(k, vector <int> (n));
for(int i = 0;i < k;i++){
int sm = 0;
for(int j = 0;j < n;j++){
if(a[j] == i)sm++;
pre[i][j] = sm;
}
}
int mn = 1e9,st = -1,en = 0;
while(en < n){
bool ps = true;
for(int j = 0;j < k;j++){
if(st == -1){
if(pre[j][en] < nm[j]){
ps = 0;
}
}
else{
if(pre[j][en] - pre[j][st] < nm[j]){
ps = 0;
}
}
}
if(ps){
mn = min(mn, en - st);
st++;
}
else{
en++;
}
}
if(st == -1){
cout<<"impossible";
}
else{
cout<<mn;
}
cout<<'\n';
}
signed main(){
cin.tie(0) -> sync_with_stdio(0);
int qu;
qu = 1;
while(qu--){
solve();
}
return 0;
}
