#include <bits/stdc++.h>
using namespace std;
int main() {
int n, k, r;
cin >> n >> k >> r;
vector<int> dna(n);
for (int i = 0; i < n; i++)
cin >> dna[i];
vector<int> req(k, -1e9);
for (int i = 0; i < r; i++) {
int b, q;
cin >> b >> q;
req[b] = q;
}
int satisfied_count = 0;
for (int i = 0; i < k; i++)
if (req[i] < 0)
satisfied_count++;
int shortest = 1e9;
int right = 0;
for (int left = 0; left < n; left++) {
while (right < n && satisfied_count != k) {
req[dna[right]]--;
if (req[dna[right]] == 0)
satisfied_count++;
right++;
}
if (satisfied_count == k && right - left < shortest) {
shortest = right - left;
}
req[dna[left]]++;
if (req[dna[left]] == 1)
satisfied_count--;
}
if (shortest == 1e9)
cout << "impossible" << endl;
else
cout << shortest << endl;
return 0;
}
