#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll inf = 1e18;
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL);
ll n, k, r; cin >> n >> k >> r;
vector<ll> v(n), cnt(k);
for(ll i = 0; i < n; i++) cin >> v[i];
for(ll i = 0; i < r; i++){
ll a, c; cin >> a >> c;
cnt[a] = -c;
}
ll b = 0, tot = 0, ans = inf;
for(ll a = 0; a < n; a++){
if(a) {
cnt[v[a-1]]--;
if(cnt[v[a-1]] < 0) tot--;
}
while(tot < r && b < n) {
cnt[v[b]]++;
if(cnt[v[b]] == 0) tot++;
b++;
}
if(tot == r) ans = min(ans, (b - a));
}
if(ans == inf) cout << "impossible";
else cout << ans;
}
