#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
const ll mod=1e9+7;
const ll maxn=2e5+5;
const int INF=1e9;
#define ok ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define fi first
#define se second
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define endl '\n'
int n, k, r, arr[maxn], cnt[maxn], hrs[maxn], x, y, ans=INF, ls=1, tot;
bool use[maxn];
int main() {
ok
cin >> n >> k >> r;
for(int i=1; i<=n; i++) {
cin >> arr[i];
}
for(int i=1; i<=r; i++) {
cin >> x >> y;
hrs[x]=y;
}
for(int i=1; i<=n; i++) {
while(tot<r && ls<=n) {
cnt[arr[ls]]++;
if(!use[arr[ls]] && cnt[arr[ls]]>=hrs[arr[ls]] && hrs[arr[ls]]) {
tot++;
use[arr[ls]]=1;
}
ls++;
}
if(tot==r) {
ans=min(ans, ls-i);
}
cnt[arr[i]]--;
if(use[arr[i]] && cnt[arr[i]]<hrs[arr[i]]) {
tot--;
use[arr[i]]=0;
}
}
if(ans==INF) cout << "impossible";
else cout << ans;
}
