#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for(int i=a; i<=b; ++i)
#define ll long long
#define sz(A) (int)(A.size())
#define pb push_back
#define eb emplace_back
#define V vector
#define pi pair<int, int>
#define f first
#define s second
const int inf=1e9;
int res=inf;
int n, k, r;
V<int> A, stan, needed;
int main() {
cin.tie(0) -> ios_base::sync_with_stdio(0);
cin >> n >> k >> r;
A.resize(n+1);
needed.resize(k+1);
stan.resize(k+1);
FOR(i, 1, n) cin >> A[i];
set<pi> secik;
int co, ile;
FOR(i, 1, r) {
cin >> co >> ile;
if(ile<=0) continue;
needed[co]=ile;
secik.insert({co, ile});
}
// int l=1;
int r=1;
stan[A[1]]++;
auto it = secik.find({A[1], needed[A[1]]});
if(it!=secik.end()) {
pi dane = *it;
dane.s--;
secik.erase(it);
if(dane.s!=0) secik.insert(dane);
}
while(!secik.empty() && r<n) {
++r;
auto it = secik.find({A[r], needed[A[r]]-stan[A[r]]});
stan[A[r]]++;
if(it!=secik.end()) {
pi dane = *it;
dane.s--;
secik.erase(it);
if(dane.s!=0) secik.insert(dane);
}
}
if(!secik.empty()) {
cout << "impossible\n";
return 0;
}
res=min(res, r);
int l=1;
while(l<=n) {
stan[A[l]]--;
while(r<n && stan[A[l]]<needed[A[l]]) {
++r;
stan[A[r]]++;
}
if(stan[A[l]]<needed[A[l]]) break;
++l;
res=min(res, r-l+1);
}
cout << res << '\n';
}
