#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define pb push_back
#define F first
#define S second
#define endl "\n"
const int INF = 1e9+10;
const int MOD = 1e9+7;
int n, k, t;
int v[200020];
int need[200020];
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> k >> t;
for(int i = 0; i < n; i++) {
cin >> v[i];
}
for(int i = 0; i < t; i++) {
int a, b; cin >> a >> b;
need[a] = b;
}
int l = 0, r = 0, ok = 0;
int cnt[200020] = {};
bool okay[200020] = {};
cnt[v[r]]++;
int resp = INF;
if(need[v[r]] != 0 and cnt[v[r]] >= need[v[r]]) {
ok++;
okay[v[r]] = true;
}
while(r < n) {
// cout << l << " " << r << endl;
// cout << v[l] << " " << v[r] << endl;
// cout << ok << endl << endl;
if(ok == t) {
resp = min(resp, r - l + 1);
cnt[v[l]]--;
if(need[v[l]] and cnt[v[l]] < need[v[l]] and okay[v[l]]) {
ok--;
okay[v[l]] = false;
}
l++;
} else {
r++;
cnt[v[r]]++;
if(need[v[r]] and cnt[v[r]] >= need[v[r]] and !okay[v[r]]) {
ok++;
okay[v[r]] = true;
}
}
}
if(resp == INF) cout << "impossible" << endl;
else cout << resp << endl;
return 0;
}
