#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int const N = 2e5+3;
set<int>s;
int reqs[N] , arr[N] , cnt[N] , tmp[N];
int n , k , q , a , b;
bool check(int x)
{
s.clear();
memset(tmp , 0 , sizeof tmp);
int r = x;
for(int i = 0 ; i < x ; i++)
{
tmp[arr[i]]++;
}
for(int i = 0 ; i < k ; i++)
{
if(reqs[i]>tmp[i])
s.insert(i);
}
if(s.empty())
return true;
set<int>::iterator it;
while(r<n)
{
tmp[arr[r]]++;
tmp[arr[r-x]]--;
if(tmp[arr[r]]>=reqs[arr[r]] && s.find(arr[r])!=s.end())
{
it=s.find(arr[r]);
s.erase(it);
}
if(tmp[arr[r-x]]<reqs[arr[r-x]]&&s.find(arr[r-x])==s.end())
{
s.insert(arr[r-x]);
}
if(s.empty())
return true;
r++;
}
return false;
}
int main()
{
cin >> n >> k >> q;
for(int i = 0 ; i < n ;i++)
{
cin >> arr[i];
cnt[arr[i]]++;
}
bool flag =true;
int l = 0 , r = n , mid;
while(q--)
{
cin >> a >> b ;
reqs[a]=b;
l+=b;
if(reqs[a]>cnt[a])
flag=false;
}
if(!flag)
{
cout << "impossible";
return 0;
}
int ans=n;
while(l<=r)
{
mid=(l+r)>>1;
//cout << mid << "\n";
if(check(mid))
{
ans=min(ans , mid);
r=mid-1;
}
else
l=mid+1;
}
cout << ans ;
return 0;
}
