#include <bits/stdc++.h>
#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define uniq(x) x.erase(unique(all(x)), x.end())
#define rall(x) x.rbegin(), x.rend()
//#define int long long
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;
void setIO() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
}
int32_t main() {
setIO();
int n, k, r;
cin >> n >> k >> r;
vector<int> v(n);
for(int &x : v) cin >> x;
vector<int> need(k, 0);
vector<bool> vis(k, 0);
for(int i=0; i<r; i++) {
int a, b;
cin >> a >> b;
need[a] = b;
vis[a] = 1;
}
int ans = 1e9;
vector<int> cnt(k, 0);
int ok = 0;
int j=0;
for(int i=0; i<n; i++) {
while(j < n && ok < r) {
cnt[v[j]]++;
if(vis[v[j]]) ok += (cnt[v[j]] == need[v[j]]);
j++;
}
//cout << i+1 << " " << j << '\n';
if(ok == r) ans = min(ans, j - i);
cnt[v[i]]--;
if(vis[v[i]]) ok -= (cnt[v[i]] == need[v[i]] - 1);
}
if(ans == 1e9) cout << "impossible\n";
else cout << ans << '\n';
return 0;
}
