#include "bits/stdc++.h"
using namespace std;
/*
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using ordered_set = tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>;
*/
#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()
using ll = long long;
const int mod = 1e9+7;
void solve(int tc) {
int n, k, r;
cin >> n >> k >> r;
vector<int> v(n);
for (auto &x : v) cin >> x;
int nreq = n-r;
vector<int> a(n);
while (r--) {
int b, q;
cin >> b >> q;
a[b] = q;
}
int ans = 1e9;
int l = 0;
r = 0;
vector<int> used(n);
while (r < n) {
++used[v[r]];
if (used[v[r]] == a[v[r]]) {
++nreq;
}
while (used[v[l]] > a[v[l]]) {
used[v[l]]--;
++l;
}
if (nreq == n) ans = min(ans, r-l+1);
++r;
}
if (ans == 1e9) cout << "impossible\n";
else cout << ans << '\n';
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
int tc = 1;
//cin >> tc;
for (int i = 1; i <= tc; ++i) solve(i);
return 0;
}
