#include <iostream>
#include <vector>
#include <utility>
#include <algorithm>
#include <iomanip>
int main(){
int n, k, r;
std::cin >> n >> k >> r;
std::vector<int> nucleobase(n);
std::vector<int> frequency(k);
for(int i = 0; i < n; ++i) {
std::cin >> nucleobase[i];
}
for(int i = 0; i < r; ++i) {
int x, f;
std::cin >> x >> f;
frequency[x] += f;
}
auto add = [&](int x, std::vector<int> &frequency_aux, int &qtd_ok) {
frequency_aux[x]++;
if(frequency_aux[x] == frequency[x] and frequency[x] > 0) {
qtd_ok++;
}
};
auto sub = [&](int x, std::vector<int> &frequency_aux, int &qtd_ok) {
if(frequency_aux[x] == frequency[x] and frequency[x] > 0) {
qtd_ok--;
}
frequency_aux[x]--;
};
auto check = [&](int window_size) {
std::vector<int> frequency_aux(k);
int qtd_ok = 0;
for(int i = 0; i < window_size; ++i) {
add(nucleobase[i], frequency_aux, qtd_ok);
}
if(qtd_ok == r) {
return true;
}
for(int i = window_size; i < n; ++i) {
sub(nucleobase[i - window_size], frequency_aux, qtd_ok);
add(nucleobase[i], frequency_aux, qtd_ok);
if(qtd_ok == r) {
return true;
}
}
return false;
};
int lo = 0, hi = n, ans = -1;
while(lo <= hi) {
int middle = (lo + hi) / 2;
if(check(middle)) {
hi = middle - 1;
ans = middle;
} else {
lo = middle + 1;
}
}
if(ans == -1) {
std::cout << "impossible\n";
} else {
std::cout << ans << '\n';
}
return 0;
}
