#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define xx first
#define yy second
#define MAXN 200010
using namespace std;
int n, k, r, a[MAXN];
set<int> svi[MAXN];
set<int>::iterator it[MAXN];
int kolko[MAXN], ress;
int main() {
cin>>n>>k>>r;
for (int i=0; i<n; i++)
{
cin>>a[i];
svi[a[i]].insert(i);
}
for (int i=0; i<r; i++)
{
int b, q; cin>>b>>q;
kolko[b]=q;
}
int r=-1;
for (int i=0; i<n; i++) {
if (kolko[i] == 0) continue;
int pom = kolko[i];
it[i] = svi[i].begin();
while (pom-1)
{
//cout<<i<<" "<<*it[i]<<endl;
pom--;
it[i]++;
if (it[i]==svi[i].end()) { cout<<"impossible"; exit(0); }
}
//cout<<i<<" "<<*it[i]<<endl;
r=max(r, *(it[i]));
}
//cout<<"ee "<<r<<endl;
ress=r+1;
for (int i=0; i<n; i++)
{
if (kolko[a[i]]==0) { ress=min(ress, r-i); continue; }
it[a[i]]++;
if (it[a[i]]==svi[a[i]].end()) break;
r=max(r, *(it[a[i]]));
ress=min(ress, r-i);
}
cout<<ress;
}
