#include<bits/stdc++.h>
using namespace std;
int main(){
int N,K,R;cin>>N>>K>>R;
vector<int> nums(N);
int occ[K];
int wantedOcc[K];
for(int i = 0 ; i <K;i++)occ[i]=wantedOcc[i]=0;
for(int i = 0 ; i <N;i++){cin>>nums[i];}
for(int i=0;i<R;i++){
int nuc,w;cin>>nuc>>w;
wantedOcc[nuc]=w;
}
int ans = N+1;
int left=0;
int nbGood=0;
for(int p=0;p<N;p++){
int val=nums[p];
if(wantedOcc[val]==0)continue;
occ[val]++;
if(occ[val]==wantedOcc[val]){
nbGood++;
}
while(nbGood==R && left<N && (wantedOcc[nums[left]]==0 || occ[nums[left]]-1>=wantedOcc[nums[left]])){
int val2 = nums[left];
occ[nums[left]]--;
left++;
if(wantedOcc[val2]==0)continue;
}
if(nbGood==R){
ans = min(ans,p-left+1);
}
}
if(ans==N+1){
cout<<"impossible"<<endl;
}else{
cout<<ans<<endl;
}
return 0;
}
