#include <bits/stdc++.h>
using namespace std;
#define fast ios::sync_with_stdio(0);cin.tie(0);
typedef long long ll;
#define f first
#define s second
#define MOD 1000000007
#define LOGN 20
#define MAXN 100005
vector<vector<int>> pref;
vector<int> DNA;
int main() {
fast
int N, K, R;
cin >> N >> K >> R;
DNA = vector<int>(N+1);
for (int i = 1; i <= N; i++)
cin >> DNA[i];
pref = vector<vector<int>>(R, vector<int>(N+1, 0));
vector<pair<int,int>> req(R);
for (int i = 0; i < R; i++)
cin >> req[i].f >> req[i].s;
for (int i = 1; i <= N; i++) {
for (int ch = 0; ch < R; ch++)
pref[ch][i] = pref[ch][i-1] + (DNA[i] == req[ch].f);
}
int res = 1e7;
for (int i = 1; i <= N; i++) {
int ans = 1e7;
for (int ch = 0; ch < R; ch++) {
if (pref[ch][i] < req[ch].s) {
ans = -1;
break;
}
int q = upper_bound(pref[ch].begin(), pref[ch].end(), pref[ch][i] - req[ch].s) - pref[ch].begin() - 1;
ans = min(ans, q);
}
if (ans == -1)
continue;
else
res = min(res, i-ans+1);
}
if (res == 1e7)
cout << "impossible\n";
else
cout << res-1 << "\n";
}
