#include <bits/stdc++.h>
using namespace std;
const int maxn=2*1e5+10;
const int inf=1e8;
int v[maxn], nucleo[maxn], qnt[maxn];
int main(){
int n,k,r;
cin >> n>> k>> r;
int rest=r;
int res=inf;
for(int i=0; i<n; i++)cin >> v[i];
for(int i=1; i<=r; i++){
int a,b;
cin >> a >> b;
nucleo[a]=b;
}
int i=0,f=0;
int y=v[i];
qnt[y]++;
if(nucleo[0]!=0 and qnt[y]==nucleo[0]) rest--;
while(i<n and f<n and i<=f){
if(rest==0){
res=min(res,f-i+1);
int x=v[i];
qnt[x]--;
if(nucleo[x]!=0 and qnt[x]==nucleo[x]-1) rest++;
i++;
}
else{
f++;
int x=v[f];
qnt[x]++;
if(nucleo[x]!=0 and nucleo[x]==qnt[x]) rest--;
}
}
if(res==inf)cout << "impossible"<<endl;
else cout << res<< endl;
return 0;
}
