#include "bits/stdc++.h"
using namespace std;
#ifdef Nero
#include "Deb.h"
#else
#define deb(...)
#endif
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, k, r;
cin >> n >> k >> r;
vector<int> a(n);
for (int i = 0; i < n; ++i) {
cin >> a[i];
}
vector<int> c(k, -1);
for (int i = 0; i < r; ++i) {
int b, q;
cin >> b >> q;
c[b] = q;
}
int ok = k - r;
vector<int> cnt(k);
auto add = [&](int ind, int v) {
ok -= cnt[a[ind]] >= c[a[ind]];
cnt[a[ind]] += v;
ok += cnt[a[ind]] >= c[a[ind]];
};
int ans = n + 1;
for (int pl = 0, pr = 0; pl < n; ++pl) {//[l, r)
pr = max(pr, pl);
while (pr < n && ok < k) {
add(pr, 1);
pr++;
}
if (ok == k) {
ans = min(ans, pr - pl);
}
add(pl, -1);
}
if (ans == n + 1) {
cout << "impossible" << '\n';
} else {
cout << ans << '\n';
}
return 0;
}
