#include <iostream>
#include <vector>
#include <queue>
using namespace std;

int main() {
    int n, k, m;
    cin >> n >> k >> m;

    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }
    vector<int> req(k + 1, 0);
    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        req[a] = b;
    }

    int j = 0;
    int cnt = m;
    int res = 2e9;
    for(int i = 0; i < n; i++) {
        while(cnt > 0 and j < n) {
            req[v[j]]--;
            if(req[v[j]] == 0) {
                cnt--;
            }
            j++;
        }
        if(cnt == 0) {
            res = min(res, j - i);
        }
        req[v[i]]++;
        if(req[v[i]] > 0) {
            cnt++;
        }
    }
    if(res == 2e9) {
        cout << "impossible" << endl;
    }
    else {
        cout << res << endl;
    }
    return 0;
}