#include <iostream>
#include <vector>
using namespace std;
int main() {
int n, k, R;
cin >> n >> k >> R;
vector <int> v(n);
for (int i = 0; i < n; i++) {
cin >> v[i];
}
vector<int> min_count(k, 0);
int tp1, tp2;
for(int i=0;i<R;i++) {
cin >> tp1 >> tp2;
min_count[tp1] = max(min_count[tp1], tp2);
}
vector<int> count(k, 0);
count[v[0]] = 1;
int ok_count = 0;
for(int i=0;i<k;i++) {
if(count[i] >= min_count[i]) {
ok_count++;
}
}
int l = 0, r = 0;
int res = 1<<29;
while(true) {
if(ok_count == k) {
res = min(res, r - l + 1);
count[v[l]]--;
if(count[v[l]] == min_count[v[l]] - 1) {
ok_count--;
}
l++;
continue;
}
r++;
if(r == n) {
break;
}
count[v[r]]++;
if(count[v[r]] == min_count[v[r]]) {
ok_count++;
}
}
if(res == 1<<29) {
cout << "impossible";
} else {
cout << res;
}
return 0;
}
