#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define FOR(i, l, r, d) for(int i=(l); i<=(r); i+=(d))
#define szof(x) ((int)(x).size())
#define vi vector<int>
#define pii pair<int,int>
#define pb push_back
#define eb emplace_back
#define mkp make_pair
const int INF = 2147483647;
const int LNF = INF*INF;
const int MOD = 1000000007;
const int mod = 998244353;
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
const int MAX = 200010;
int n, k, r;
int arr[MAX];
int cnt[MAX];
int req[MAX];
int sat;
int lptr, rptr;
int res;
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin>>n>>k>>r;
FOR(i, 1, n, 1){
cin>>arr[i];
}
FOR(i, 1, r, 1){
int type;
cin>>type;
cin>>req[type];
}
res = INF;
lptr = 1, rptr = 0;
sat = 0;
int type;
while(lptr <= n){
while(sat < r){
rptr++;
if(rptr > n) break;
type = arr[rptr];
cnt[type]++;
if(cnt[type] == req[type]){
sat++;
}
}
if(rptr > n) break;
res = min(res, rptr - lptr + 1);
//cerr<<"["<<lptr<<", "<<rptr<<"]"<<endl;
type = arr[lptr];
if(cnt[type] == req[type]){
sat--;
}
cnt[type]--;
lptr++;
}
if(res == INF){
cout<<"impossible"<<'\n';
}
else{
cout<<res<<'\n';
}
return 0;
}
