#include<bits/stdc++.h>
using namespace std;
#define w long long
#define mod 1000000007
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
w n,k,R;
cin>>n>>k>>R;
vector<w>v(n);
for(w i=0;i<n;++i)cin>>v[i];
vector<w>needed(n);
w g=0;
for(w i=0;i<R;++i){
w z,c;
cin>>z>>c;
needed[z]=c;
g+=c;
}
w ans=n+1;
w l=1,r=n;
while(l<=r){
w m=(l+r)/2;
w cnt_of_needed=g;
vector<w>acquired(n);
for(w i=0;i<m;++i){
// cout<<v[i]<<' ';
if(needed[v[i]]>0){
if(acquired[v[i]]<needed[v[i]]){
cnt_of_needed--;
}
acquired[v[i]]++;
}
}
// cout<<endl<<cnt_of_needed;
w i=m;
while(cnt_of_needed!=0&& i<n){
if(needed[v[i]]){
if(acquired[v[i]]<needed[v[i]]){
cnt_of_needed--;
}
acquired[v[i]]++;
}
if(needed[v[i-m]]){
if(acquired[v[i-m]]<=needed[v[i-m]]){
cnt_of_needed++;
}
acquired[v[i-m]]--;
}
// cout<<i<<" : "<<m<<' '<<cnt_of_needed<<endl;
i++;
}
// cout<<m<<endl;
if(cnt_of_needed==0){
// cout<<m<<endl;
ans=min(ans,m);
r=m-1;
}else l=m+1;
// cout<<l<<endl;
}
if(ans==n+1)cout<<"impossible";
else cout<<ans;
}
