#include <bits/stdc++.h>
using namespace std;
#define max(a, b) (a > b ? a : b)
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, k, r;cin>>n>>k>>r;
int* dna = new int[n];
for (int i = 0;i < n;i++)
cin >> dna[i];
unordered_set<int> hset;
unordered_map<int, int> req;
unordered_set<int> sreq;
for (int i = 0;i < r;i++)
{
int x, y;
cin >> x >> y;
hset.emplace(x);
req[x] = y;
sreq.emplace(x);
}
int min_len = 1e9;
int j = -1;
for (int i = 0;i < n;i++)
{
if (i && hset.count(dna[i-1]))
{
req[dna[i-1]]++;
if (req[dna[i-1]] > 0)
sreq.emplace(dna[i-1]);
}
if (sreq.size())
for (j=j+1;j < n;j++)
{
if (hset.count(dna[j]))
{
req[dna[j]]--;
if (req[dna[j]] <= 0)
sreq.erase(dna[j]);
}
if (!sreq.size()) {
min_len = min(min_len, j - i + 1);
break;
}
}
else
min_len = min(min_len, j - i + 1);
}
if (min_len == 1e9)
cout << "impossible";
else if (min_len)
cout << min_len;
else if (min_len == 0)
cout << "impossible";
return 0;
}
