#include<bits/stdc++.h>
using namespace std;
typedef long double ld;
#define int long long
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
const int LIM=2e5+7;
int T[LIM], ile[LIM], R[LIM];
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n, k, r;
cin >> n >> k >> r;
rep(i, n) cin >> T[i];
int zle=0;
rep(i, r) {
int b, q;
cin >> b >> q;
R[b]=q;
if(q) ++zle;
}
int l=0, ans=LIM;
rep(i, n) {
while(l<n && zle) {
++ile[T[l]];
if(ile[T[l]]==R[T[l]]) --zle;
++l;
}
if(!zle) ans=min(ans, l-i);
if(ile[T[i]]==R[T[i]]) ++zle;
--ile[T[i]];
}
if(ans==LIM) cout << "impossible\n";
else cout << ans << '\n';
}
