#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>
class SegmentTree {
public:
void resz (int N) {
N = (1 << ((int)floor(log2(N - 1)) + 1));
this->N = N;
val.assign(2 * N, ID);
}
void update (int x, T y) {
x += N - 1;
val[x] = y;
while (x != 0) {
x = (x - 1)/2;
val[x] = merge(val[2 * x + 1], val[2 * x + 2]);
}
}
T query (int ind, const int l, const int r, int tl, int tr) {
if (tl >= l && tr <= r) {
return val[ind];
}
if (tr < l || tl > r) {
return ID;
}
return merge(query(2 * ind + 1, l, r, tl, (tl + tr)/2), query(2 * ind + 2, l, r, (tl + tr)/2 + 1, tr));
}
T query (int l, int r) {
return query(0, l, r, 0, N - 1);
}
private:
vector<T> val;
T ID = 0;
T merge (T x, T y) {
return x + y;
}
int N;
};
vector<SegmentTree<int>> st;
vector<int> arr;
vector<pair<int,int>> queries;
bool okay (int l, int r) {
int R = queries.size();
for (int i = 0; i < R; i++) {
if (st[i].query(l, r) < queries[i].second) {
return false;
}
}
return true;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int N, K, R;
cin >> N >> K >> R;
st.resize(R);
for (int i = 0; i < R; i++) {
st[i].resz(N);
}
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;
}
for (int i = 0; i < N; i++) {
for (int j = 0; j < R; j++) {
if (arr[i] == queries[j].first) {
st[j].update(i, 1);
}
}
}
int myMin = INT_MAX;
for (int i = 0; i < N; i++) {
if (!okay(i, N - 1)) {
break;
}
int l = i;
int r = N - 1;
while (l != r) {
int m = (l + r)/2;
if (okay(i, m)) {
r = m;
} else {
l = m + 1;
}
}
//cout << i << " " << l << '\n';
myMin = min(myMin, l - i + 1);
}
if (myMin == INT_MAX) {
cout << "impossible\n";
} else {
cout << myMin;
}
}
