#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define f first
#define s second
#define mid (l+r)/2.0
const int M=1e18,N=3e5+1,mod=998244353;
int pxp(int x,int p){
int ans=1;
while(p){
if(p&1)ans*=x,ans%=mod; x*=x,x%=mod,p>>=1;}
return ans;
}
void solve(){
int n,k,R;cin>>n>>k>>R;
vector<int> a(n);
map <int,int> mp;
for(int i=0;i<n;i++)cin>>a[i];
for(int i=0;i<R;i++){
int x,y;cin>>x>>y;
mp[x]=y;
}
int l=0,r=0,cnt=0,ans=M;
while(r<n){
mp[a[r]]--;
if(mp[a[r]]==0)cnt++;
r++;
while(cnt==R){
mp[a[l]]++;
if(mp[a[l]]==1)cnt--;
l++;
ans=min(ans,r-l+1);
}
}
if(ans==M)cout<<"impossible"<<'\n';
else cout<<ans<<'\n';
}
signed main(){
ios::sync_with_stdio(0), cin.tie(0); cout.tie(0);
// int t; cin>>t; while(t--)
solve();
return 0;
}
