#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define pb push_back
#define vi vector<int>
#define vl vector<ll>
#define pi pair<int, int>
#define pl pair<ll,ll>
#define all(x) (x).begin(),(x).end()
int32_t main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n,k,r;
cin >> n >> k >> r;
vi a(n);
vi cnt(k,0);
for (int i=0; i<n; i++) {
cin >> a[i];
cnt[a[i]]++;
}
vi need(k,0);
int b,c;
for (int i=0; i<r; i++) {
cin >> b >> c;
need[b]=c;
}
vi cur(k,0);
int mn=1e9;
int ok=count(all(need),0);
r=0;
for (int l=0; l<n; l++) {
while (r<n && ok<k) {
cur[a[r]]++;
if (cur[a[r]]==need[a[r]]) {
ok++;
}
r++;
}
if (ok==k) {
mn=min(mn,r-l);
}
if (cur[a[l]]==need[a[l]]) {
ok--;
}
cur[a[l]]--;
}
if (mn==1e9) {
cout << "impossible\n";
}
else {
cout << mn << '\n';
}
return 0;
}
