// 23 - 12 - 23
#include<bits/stdc++.h>
using namespace std;
#define read() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define day() time_t now = time(0);char* x = ctime(&now);cerr<<"Right Now Is : "<<x<<"\n"
#define ii pair<int,int>
#define X first
#define Y second
const long long MAX = (int)2e5 + 5;
const long long INF = (int)1e9;
const long long MOD = (int)1e9 + 7;
int n,k,r;
int req[MAX];
vector<int> adj[MAX];
int id[MAX],a[MAX];
signed main(){
read();
cin >> n >> k >> r;
for(int i = 1;i <= n;i++){
cin >> a[i];
adj[a[i]].push_back(i);
id[i] = (int)adj[a[i]].size() - 1;
}
for(int i = 1,b,q;i <= r;i++){
cin >> b >> q;
req[b] = q;
}
set<int> st;
int res = INF;
for(int i = 1;i <= n;i++){
if(req[a[i]] == 0)continue;
if(id[i] > 0 && id[i] - 1 - req[a[i]] + 1 >= 0)
st.erase(adj[a[i]][id[i] - req[a[i]]]);
if(id[i] - req[a[i]] + 1 >= 0)
st.insert(adj[a[i]][id[i] - req[a[i]] + 1]);
//cout << i << " " << st.size() << '\n';
if(st.size() == r)res = min(res,i - *st.begin() + 1);
}
if(res == INF)cout << "impossible\n";
else cout << res << '\n';
// cout << (res == INF ? "impossible" : res) << '\n';
}
