#include<bits/stdc++.h>
using namespace std;
int main(){
int n, m, q;
cin >> n >> m >> q;
int a[n+1];
for(int i = 1; i <= n; i++){
cin >> a[i];
}
int ok[m+1]={};
for(int i = 0; i < q; i++){
int x, y;
cin >> x >> y;
ok[x] = y;
}
int l = 1, r = 1, c = 0;
int cnt[m+1]={}, fix[n+1]={}, ans = 1e9;
while(l<=n&&r<=n){
if(fix[r]==0&&r<=n){
cnt[a[r]]++;
if(cnt[a[r]]==ok[a[r]]) c++;
}
if(r<=n)fix[r] = 1;
if(c==q){
ans = min(ans, r- l+1);
cnt[a[l]]--;
if(cnt[a[l]]==ok[a[l]]-1) c--;
l++;
} else r++;
}
if(ans==1e9) cout <<"impossible";
else cout << ans ;
}
