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



int main()
{
    int n, k;
    cin>>n >> k;
    int m;
    cin>>m;
    if(n > 100) {
        return 0;
    }
    vector<int> req(k + 1, 0);

    vector<int>v;

    for(int i=0; i<n; i++){
        int a;
        cin>>a;
        v.push_back(a);
    }
    int zbir=0;
    for(int j=0; j<m; j++){
    int a, b;
    //a brojot sto go barame // b za kolicina
    cin>>a>>b;
        req[a] = b;
    zbir+=b;
    }

    int min_length=2e9;
    int tmp=0;
    vector<int> t = req;

    for(int i=0; i<v.size(); i++){
        for(int j=0; j<v.size(); j++){
            tmp = 0;
            req = t;
            for(int k=i; k<=j; k++){
                        if(req[v[k]]>0){
                            req[v[k]]--;

                        }
                bool ok = true;
                for(int x = 0; x < req.size(); x++) {
                    if(req[x] != 0) {
                        ok = false;
                        break;
                    }

                }
                if(ok) {
                    min_length = min(min_length, j - i + 1);
                }
            }
        }
    }
    if(min_length == 2e9) {
        cout << "impossible";
    }
    else
    cout << min_length << endl;
    return 0;
}
/*
 5 2 2
 0 1 1 0 1
 0 1
1 1

 13 4 3
 1 1 3 2 0 1 2 0 0 0 0 3 1
 0 2
 2 1
 1 2

 5 3 1
 1 2 0 1 2
 0 2
 **/