#include <iostream>
#include <iomanip>
#include <stack>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <vector>
#include <utility>
#include <algorithm>
#include <numeric>
#include <string>
#include <cmath>
#include <random>
#include <sstream>
#include <string.h>
#include <assert.h>
#include <limits.h>
using namespace std;
#define fi first
#define se second
#define int long long
#define pb push_back
typedef pair<int,int> ii;
const int INF = 1e18;
map<int, int> cons;
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, k, r; cin >> n >> k >> r;
vector<int> a(n + 2); for (int i=1; i<=n; i++) cin >> a[i];
for (int i=1; i<=r; i++) {
int b, q; cin >> b >> q;
cons[b] = q;
}
// cout << "HERE\n";
queue<int> cur; map<int, int> rem;
int cnt = 0; int ans = INF;
map<int, int> have;
for (int i=1; i<=n; i++) {
// cout << ">> " << a[i] << " " << have[a[i]] << " " << cons[a[i]] << '\n';
if (cons.count(a[i]) && have[a[i]] < cons[a[i]]) {
cur.push(a[i]), have[a[i]]++; if (have[a[i]] == cons[a[i]]) cnt++;
}
else {
have[a[i]]++; cur.push(a[i]);
if (cur.front() == a[i])
cur.pop(), have[a[i]]--;
else
rem[a[i]]++;
}
if (cnt == r)
ans = min(ans, (int)cur.size());
while(!cur.empty() && rem[cur.front()] > 0) {
rem[cur.front()]--; have[cur.front()]--; cur.pop();
}
}
if (ans == INF) cout << "impossible";
else cout << ans;
return 0;
}
