#undef _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb push_back
#define fi first
#define si second
typedef pair<int,int> pi;
typedef tuple<int,int,int> ti;
void debug_out() {cerr<<endl;}
template <typename Head, typename... Tail>
void debug_out(Head _H, Tail... _T) {cerr<<" "<<to_string(_H);debug_out(_T...);}
#define debug(...) cerr<<"["<<#__VA_ARGS__<<"]:",debug_out(__VA_ARGS__)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MAXN = 200010, INF = 2e9;
int n, k, r;
int arr[MAXN];
int req[MAXN];
int cnt[MAXN];
set<int> bases;
int ans = INF;
void remove(int i) {
if (!req[arr[i]]) return;
--cnt[arr[i]];
if (cnt[arr[i]] < req[arr[i]]) {
if (*bases.lower_bound(arr[i]) == arr[i]) bases.erase(arr[i]);
}
}
void add(int i) {
if (!req[arr[i]]) return;
++cnt[arr[i]];
if (cnt[arr[i]] >= req[arr[i]]) bases.insert(arr[i]);
}
bool check(int i) {
if (!req[arr[i]]) return true;
return (cnt[arr[i]] > req[arr[i]]);
}
int main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> k >> r;
for (int i = 1; i <= n; ++i) cin >> arr[i];
for (int i = 1; i <= r; ++i) {
int x, y; cin >> x >> y;
req[x] = y;
}
int l = 1;
for (int i = 1; i <= n; ++i) {
add(i);
if ((int)bases.size() == r) {
while (l < i && check(l)) {
remove(l);
++l;
}
ans = min(ans, i - l + 1);
}
}
if (ans == INF) cout << "impossible";
else cout << ans;
return 0;
}
