#pragma once
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pld;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ld> vld;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<pld> vpld;
typedef vector<vi> vvi;
template<typename T> using pq = priority_queue<T>;
template<typename T> using pqg = priority_queue<T, vector<T>, greater<T>>;
#define rep0(a) for (int i = 0; i < a; ++i)
#define rep1(i, a) for (int i = 0; i < a; ++i)
#define rep2(i, a, b) for (int i = a; i <= b; ++i)
#define rep3(i, a, b, c) for (int i = a; i <= b; i+=c)
#define overload4(a, b, c, d, e, ...) e
#define rep(...) overload4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__)
#define repd0(a) for (int i = a; i >= 1; --i)
#define repd1(i, a) for (int i = a; i >= 1; --i)
#define repd2(i, a, b) for (int i = b; i >= a; --i)
#define repd3(i, a, b, c) for (int i = b; i >= a; i-=c)
#define repd(...) overload4(__VA_ARGS__, repd3, repd2, repd1, repd0)(__VA_ARGS__)
#define trav(a, x) for (auto& a : x)
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define st first
#define nd second
#define lb lower_bound
#define ub upper_bound
#define all(x) (x).begin(), (x).end()
#define ins insert
template<typename T> bool ckmin(T &a, const T &b) { return b < a ? a = b, 1 : 0; }
template<typename T> bool ckmax(T &a, const T &b) { return a < b ? a = b, 1 : 0; }
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MOD = 1e9 + 7;
const int INF = 0x3fffffff;
const ll LINF = 0x1fffffffffffffff;
const char nl = '\n';
const int MX = 1e5 + 3;
void solve() {
int n, k, r; cin >> n >> k >> r;
vi a(n+1), ask(k, 0), cur(k+1, 0); rep(i, 1, n) cin >> a[i];
int ans = INF, cnt = 0, idx = 1;
rep(i, 1, r) {
int b, q; cin >> b >> q;
ask[b] = q;
}
rep(i, 1, n) {
while (idx < n && cnt != r) {
int now = a[idx];
cur[now]++;
if (cur[now] == ask[now]) cnt++;
idx++;
}
if (cnt == r) ckmin(ans, idx-i);
int now = a[i];
if (cur[now] == ask[now]) cnt--;
cur[now]--;
}
cout << (ans == INF ? "impossible" : to_string(ans)) << nl;
}
int main(int argc, char* argv[]) {
ios_base::sync_with_stdio(0); cin.tie(NULL);
int t = 1;
// cin >> t;
while (t--) { solve(); }
return 0;
}
