#include <bits/stdc++.h>
#define ll long long
#define ar array
#define db double
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define rint(l, r) uniform_int_distribution<int>(l, r)(rng)
template<typename T> bool ckmin(T &a, const T &b) { return a > b ? a = b, 1 : 0; }
template<typename T> bool ckmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }
void test_case() {
int n, k, m;
cin >> n >> k >> m;
vector<int> req(k), a(n);
for (int &x : a) cin >> x;
for (int i = 0; i < m; i++) {
int x, y; cin >> x >> y;
req[x] = y;
}
int good = k - m, to = -1;
vector<int> have(k);
int ans = 1e9;
for (int i = 0; i < n; i++) {
while (good < k && to+1 < n) {
if (++have[a[to+1]] == req[a[to+1]]) {
good++;
}
to++;
}
if (good == k) {
ckmin(ans, to - i + 1);
}
else break;
assert(have[a[i]] >= req[a[i]]);
if (have[a[i]]-- == req[a[i]]) good--;
}
if (ans == 1e9) cout << "impossible\n";
else cout << ans << '\n';
}
int main() {
cin.tie(0)->sync_with_stdio(0);
int t = 1;
// cin >> t;
while (t--) test_case();
}
