#include<iostream>
#include<stdio.h>
#include<math.h>
#include<map>
#include<string>
#include<algorithm>
#include<vector>
#include<string.h>
#include<utility>
#include<set>
#include<cmath>
#include<queue>
#include<deque>
#include<functional>
#include<stack>
#include<limits.h>
#include<iomanip>
#include<unordered_map>
#include<numeric>
#include<tuple>
#include<bitset>
using namespace std;
#define MOD 1000000007
#define int long long
#define ss second
#define ff first
#define endl '\n'
typedef pair<int,int> pp;
signed main(){
// freopen("file.in", "r", stdin);
// freopen("file.out", "w", stdout);
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,k,r; cin>>n>>k>>r;
vector<int> a(n+1),mp(k+1,-1),fq(k+1);
for(int i=1; i<=n; i++) cin>>a[i];
for(int i=1; i<=r; i++){
int b,q; cin>>b>>q;
mp[b]=q;
}
int ans=1e18,sum=0;
for(int i=1,j=1; i<=n; i++){
fq[a[i]]++;
if(fq[a[i]]==mp[a[i]]&&mp[a[i]]!=-1) sum++;
while(sum==r){
ans=min(ans,i-j+1);
fq[a[j]]--;
if(fq[a[j]]<mp[a[j]]&&mp[a[j]]!=-1) sum--;
j++;
}
}
if(ans==1e18) cout<<"impossible";
else cout<<ans;
return 0;
}
