#include <cmath>
#include <iostream>
#include <set>
#include <climits>
#include <algorithm>
#include <cassert>
#include <vector>
#include <iomanip>
#include <type_traits>
#include <string>
#include <queue>
#include <map>
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
typedef long long ll;
using namespace std;
template<class T> struct Seg { // comb(ID,b) = b
const T ID = 1; T comb(T a, T b) { return min(a,b); }
int n; vector<T> seg;
void init(int _n) { n = _n; seg.assign(2*n,ID); }
void pull(int p) { seg[p] = comb(seg[2*p],seg[2*p+1]); }
void upd(int p, T val) { // set val at position p
seg[p += n] = val; for (p /= 2; p; p /= 2) pull(p); }
T query(int l, int r) { // sum on interval [l, r]
T ra = ID, rb = ID;
for (l += n, r += n+1; l < r; l /= 2, r /= 2) {
if (l&1) ra = comb(ra,seg[l++]);
if (r&1) rb = comb(seg[--r],rb);
}
return comb(ra,rb);
}
};
vector<int> arr;
vector<pair<int,int>> queries;
Seg<int> valid;
vector<int> cnt;
map<int,int> myMap;
void updater (int x, int d) {
if (!myMap.count(arr[x])) {
return;
}
cnt[myMap[arr[x]]] += d;
valid.upd(myMap[arr[x]], cnt[myMap[arr[x]]] >= queries[myMap[arr[x]]].second);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int N, K, R;
cin >> N >> K >> R;
arr.resize(N);
for (int i = 0; i < N; i++) {
cin >> arr[i];
}
queries.resize(R);
for (int i = 0; i < R; i++) {
cin >> queries[i].first >> queries[i].second;
myMap[queries[i].first] = i;
}
cnt.resize(R);
valid.init(R + 1);
for (int i = 0; i <= R; i++) {
valid.upd(i, 0);
}
int l = -1;
int r = -1;
int myMin = INT_MAX;
while (l + 1 < N && r < N) {
if (l != -1) {
updater(l, -1);
}
l++;
while (r != N - 1 && !valid.query(0, R - 1)) {
updater(r + 1, 1);
r++;
}
if (!valid.query(0, R - 1)) {
break;
}
myMin = min(myMin, r - l + 1);
}
if (myMin == INT_MAX) {
cout << "impossible\n";
} else {
cout << myMin;
}
//cout << ((myMin == INT_MAX) ? "impossible" : myMin);
}
