#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
using namespace std;
int main() {
bool ans = true;
int n,k,r;
cin >> n >> k >> r;
vector<int> a(n);
vector<int> needed(n, 0);
vector<int> count(n, 0);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
while(r--) {
int x,y;
cin >> x >> y;
needed[x] = y;
}
for(int i = 1; i < n; i++) {
for(int j = 0; j < n; j++) {
for(int l = j; l < n; l++) {
count[a[l]]++;
}
}
for(int j = 0; j < k; j++) {
if(count[j] != needed[j]) {
ans = false;
}
}
if(ans) {
cout << i;
return 0;
}
}
cout << "impossible";
}
