#include <bits/stdc++.h>
using namespace std;
int main()
{
// Use fast I/O to handle N up to 200,000 within the time limit
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, k, r;
if (!(cin >> n >> k >> r)) return 0;
// Read the DNA sequence
vector<int> v(n);
for(int i = 0; i < n; i++)
cin >> v[i];
// Store the requirements.
// req[b] = quantity needed for nucleobase b
vector<int> req(k, 0);
for(int i = 0; i < r; i++) {
int b, q;
cin >> b >> q;
req[b] = q;
}
// Vector to store counts of nucleobases in the current window
vector<int> cnt(k, 0);
int i = 0; // Left pointer of the window
int formed = 0; // How many distinct nucleobase requirements are currently satisfied
int res = n + 1; // Initialize result to a value larger than possible (Infinity)
// j is the Right pointer of the window
for(int j = 0; j < n; j++)
{
// 1. Expand the window to the right
int current_char = v[j];
cnt[current_char]++;
// If this nucleobase has a requirement and we just reached it
if(req[current_char] > 0 && cnt[current_char] == req[current_char]) {
formed++;
}
// 2. Shrink the window from the left as long as requirements are met
while(formed == r)
{
// We have a valid window, update the minimum length
res = min(res, j - i + 1);
// Remove the leftmost character
int left_char = v[i];
cnt[left_char]--;
// If the count drops below the requirement, we no longer satisfy this requirement
if(req[left_char] > 0 && cnt[left_char] < req[left_char]) {
formed--;
}
// Move left pointer forward
i++;
}
}
// Output the result
if(res > n)
cout << "impossible";
else
cout << res;
return 0;
}
