#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
typedef long long ll;
typedef pair<int,int> ii;
int n, k, r;
vector<int> a;
map<int,int> need, cnt;
bool can(int mid) {
cnt.clear();
int full = 0;
for (int i = 1; i <= n; i++) {
cnt[a[i]]++;
if (need.count(a[i]) && cnt[a[i]] == need[a[i]]) full++;
if (i-mid >= 1) {
cnt[a[i-mid]]--;
if (need.count(a[i-mid]) && cnt[a[i-mid]] == need[a[i-mid]]-1) full--;
}
if (i >= mid && full >= r) return 1;
}
return 0;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> k >> r;
a = vector<int>(n+2);
for (int i = 1; i <= n; i++) cin >> a[i];
for (int i = 1; i <= r; i++) {
int b, q; cin >> b >> q;
need[b] = q;
}
int ans = -1;
for (int l = 1, r = n; l <= r; ) {
int mid = (l+r)/2;
// cout << mid << " -> " << can(mid) << '\n';
if (can(mid)) {
ans = mid;
r = mid-1;
}
else l = mid+1;
}
if (ans == -1) cout << "impossible\n";
else cout << ans << '\n';
return 0;
}
