#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
#define all(x) (x).begin(),(x).end()
#define X first
#define Y second
#define sep ' '
#define endl '\n'
#define debug(x) cerr << #x << ": " << x << endl;
const ll MAXN = 1e6 + 10;
int R[MAXN], n, k, r, ans = MAXN, A[MAXN];
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n >> k >> r;
for (int i = 1; i <= n; i++) cin >> A[i];
for (int i = 1; i <= r; i++) {
int x, y;
cin >> x >> y;
R[x] = y;
}
int p = 1;
for (int i = 1; i <= n; i++) {
if (R[A[i]] == 1) r--;
R[A[i]]--;
while (R[A[p]] < 0)
R[A[p++]]++;
if (r <= 0) ans = min(ans, i - p + 1);
}
cout << (ans == MAXN ? "impossible" : to_string(ans)) << endl;
return 0;
}
