#include <bits/stdc++.h>
using namespace std;
#define lli long long int
#define X first
#define Y second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define pii pair<int, int>
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define test(args...) abc("[" + string(#args) + "]", args)
void abc() {cerr << endl;}
template <typename T, typename ...U> void abc(T a, U ...b) {
cerr << a << ' ', abc(b...);
}
template <typename T> void printv(T l, T r) {
while (l != r) cerr << *l << " \n"[++l == r];
}
const int mod = 1e9 + 7, N = 200000;
int main () {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m, k;
cin >> n >> m >> k;
vector <int> a(n), need(m, 0);
for (int i = 0; i < n; ++i) cin >> a[i];
for (int i = 0, v, c; i < k; ++i) {
cin >> v >> c;
need[v] = c;
}
vector <int> cnt(m, 0);
int ok = k, ans = n + 1;
auto add = [&](int v) {
cnt[v]++;
if (cnt[v] == need[v]) ok--;
};
auto del = [&](int v) {
if (cnt[v] == need[v]) ok++;
cnt[v]--;
};
for (int i = 0, j = 0; i < n; ++i) {
while (ok && j < n) {
add(a[j++]);
}
if (!ok) ans = min(ans, j - i);
del(a[i]);
}
if (ans == n + 1) cout << "impossible\n";
else cout << ans << endl;
}
