#include<bits/stdc++.h>
using namespace std;
#define int int64_t
#define pb push_back
#define st first
#define nd second
#define pii pair<int, int>
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
const int MAXN = 200009;
int cnt[MAXN];
int sum[MAXN];
int cur[MAXN];
int tab[MAXN];
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, k, r;
cin >> n >> k >> r;
for(int i=0;i<n;i++) {
cin >> tab[i];
sum[tab[i]]++;
}
for(int i=0;i<r;i++) {
int a, b;
cin >> a >> b;
cnt[a] = b;
if(sum[a]<b) {
cout << "impossible\n";
return 0;
}
}
int R = -1;
int bad_cnt = r;
int ans = 1e9;
for(int L=0;L<n;L++) {
while(R+1<n && bad_cnt) {
R++;
cur[tab[R]]++;
if(cur[tab[R]]==cnt[tab[R]]) {
bad_cnt--;
}
}
if(bad_cnt==0) {
ans = min(ans, R-L+1);
}
cur[tab[L]]--;
if(cur[tab[L]]==cnt[tab[L]]-1) {
bad_cnt++;
}
}
cout << ans << "\n";
}
