#include <bits/stdc++.h>
using namespace std;
const int maxn = 200000; // R, K <= N
const int INF = 2e9;
int n, // length of real DNA
k, // alphabet size
r; // number of minimum quantities
int min_quant[maxn];
int cur_quant[maxn];
int dna[maxn];
int current_satisfied;
int ans = INF;
int main() {
// freopen("main.in", "r", stdin);
cin >> n >> k >> r;
for (int i = 0; i < n; i++) cin >> dna[i];
for (int i = 0; i < r; i++) {
int a; cin >> a;
cin >> min_quant[a];
}
for (int i = 0; i < k; i++)
current_satisfied += cur_quant[i] >= min_quant[i];
int l = 0;
for (int i = 0; i < n; i++) { // [l, i] inclusive
// add new
cur_quant[dna[i]]++;
if (cur_quant[dna[i]] == min_quant[dna[i]])
current_satisfied++;
// remove as many as possible
while (current_satisfied == k && l <= i) {
ans = min(ans, i - l + 1);
if (cur_quant[dna[l]] == min_quant[dna[l]]) current_satisfied--;
cur_quant[dna[l]]--;
l++;
}
}
if (ans == INF) { cout << "impossible" << endl; return 0; }
cout << ans << endl;
return 0;
}
