#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, k, r;
cin >> n >> k >> r;
int ans = INT_MAX;
vector<int> a(n);
for (int& i : a) cin >> i;
vector<int> has(k), need(k), cnt(k);
for (int i = 0; i < r; i++)
{
int b, q;
cin >> b >> q;
has[b] = 1;
need[b] = q;
}
int cur = 0;
for (int i = 0, j = 0; j < n; j++)
{
if (has[a[j]])
{
cnt[a[j]]++;
if (cnt[a[j]] == need[a[j]]) cur++;
}
while (cur == r)
{
if (has[a[i]])
{
cnt[a[i]]--;
if (cnt[a[i]] < need[a[i]]) cur--;
}
i++;
}
if (i) ans = min(ans, j - i + 2);
}
if (ans == INT_MAX) cout << "impossible";
else cout << ans;
cout << '\n';
return 0;
}
