#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int N, K, R;
cin >> N >> K >> R;
vector<int> A;
int req[K], curr[K];
int ans = 0;
fill(req, req+K, 0);
fill(curr, curr+K, 0);
for (int i=0; i<N; ++i) {
int n;
cin >> n;
A.emplace_back(n);
}
for (int i=0; i<R; ++i) {
int n, amt;
cin >> n >> amt;
req[n] = amt;
}
int req_met = 0;
if (R == 0) {
cout << 1;
return 0;
}
int l = 0, r = 0;
while (l < N) {
if (req_met < R && r<N) {
curr[A[r]]++;
if (req[A[r]] > 0 && curr[A[r]] == req[A[r]]) req_met++;
r++;
}
else {
if (req_met >= R) {
if (ans == 0) ans = r - l;
else ans = min(ans, r-l);
}
curr[A[l]]--;
if (req[A[l]] > 0 && curr[A[l]] < req[A[l]]) req_met--;
l++;
}
}
if (ans != 0) cout << ans;
else cout << "impossible";
return 0;
}
