#include <bits/stdc++.h>
#define int long long
using namespace std;
constexpr int N = 2e5+5;
int n, k, r;
int d[N];
int cnt[N], req[N];
int sated;
void solve() {
for (int i = 0; i < k; ++i) {
sated += req[i] == 0;
}
int j = 1, res = n + 1;
for (int i = 1; i <= n; ++i) {
++cnt[d[i]];
if (cnt[d[i]] == req[d[i]]) ++sated;
while (j < i && cnt[d[j]] - 1 >= req[d[j]]) {
--cnt[d[j]];
++j;
}
if (sated == k) res = min(res, i - j + 1);
}
if (res == n + 1) cout << "impossible";
else cout << res;
}
signed main() {
cin.tie(0)->sync_with_stdio(0);
cin >> n >> k >> r;
for (int i = 1; i <= n; ++i) {
cin >> d[i];
}
for (int i = 1; i <= r; ++i) {
int b, q; cin >> b >> q;
req[b] = q;
}
solve();
}
