#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myrand(ll B){
return (ull)rng() % B;
}
inline double time() {
return static_cast<long double>(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count()) * 1e-9;
}
int main() {
cin.tie(nullptr);
ios::sync_with_stdio(false);
int n,k,q; cin >> n >> k >> q;
vector<int> a(n);
for (int i = 0; i < n; ++i) {
cin >> a[i];
}
vector<int> b(k);
for (int i = 0; i < q; ++i) {
int x,y; cin >> x >> y;
b[x] = y;
}
vector<int> c(k);
int cnt = 0;
for (int i = 0; i < k; ++i) {
if(c[i] >= b[i]) cnt++;
}
int res = n+1;
int r = 0;
for (int l = 0; l < n; ++l) {
while(r < n and cnt < k){
c[a[r]]++;
if(c[a[r]] == b[a[r]]) cnt++;
r++;
}
if(cnt == k){
res = min(res, r-l);
}
if(c[a[l]] == b[a[l]]) cnt--;
c[a[l]]--;
}
if(res == n+1){
cout << "impossible" << endl;
}
else{
cout << res << endl;
}
}
