#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define FOR(i, x, y) for (int i = x; i < y; i++)
#define MOD 1000000007
typedef long long ll;
using namespace std;
int n, k, r;
int a[200001], req[200001], cnt[200001];
bool check(int len) {
int num_fulfilled = 0;
fill(cnt, cnt + n, 0);
FOR(i, 0, len) {
cnt[a[i]]++;
if (cnt[a[i]] == req[a[i]]) num_fulfilled++;
}
if (num_fulfilled == r) return true;
FOR(i, len, n) {
if (cnt[a[i - len]] == req[a[i - len]]) num_fulfilled--;
cnt[a[i - len]]--;
cnt[a[i]]++;
if (cnt[a[i]] == req[a[i]]) num_fulfilled++;
if (num_fulfilled == r) return true;
}
return false;
}
int main() {
iostream::sync_with_stdio(false);
cin.tie(0);
cin >> n >> k >> r;
FOR(i, 0, n) cin >> a[i];
FOR(i, 0, r) {
int x;
cin >> x >> req[x];
}
int l = 1, r = n;
while (l != r) {
int mid = (l + r) / 2;
if (check(mid)) r = mid;
else l = mid + 1;
}
if (check(n)) cout << l << '\n';
else cout << "impossible\n";
return 0;
}
