#include <bits/stdc++.h>
using namespace std;
struct SegTree {
vector<int> seg;
int MAX;
SegTree(int N) {
int i;
for(i=1;i<2*N;i*=2) {}
seg.resize(i);
MAX = i;
for(i=MAX/2;i<MAX;i++) seg[i] = i - MAX/2;
}
void cons() {
for(int i = MAX/2-1;i>=1;i--) {
seg[i] = min(seg[2*i], seg[2*i+1]);
}
}
void prop(int n, int ns, int ne) {
if(n<MAX/2) {
seg[2*n] = max(seg[2*n], seg[n]);
seg[2*n+1] = max(seg[2*n+1], seg[n]);
}
}
void add(int s, int e, int n, int ns, int ne) {
prop(n,ns,ne);
if(e<=ns||ne<=s) return;
if(s<=ns&&ne<=e) {
seg[n] = 1e9;
prop(n,ns,ne);
return;
}
int mid = ns + ne >> 1;
add(s, e, 2*n, ns, mid);
add(s, e, 2*n+1, mid, ne);
if(n<MAX/2) seg[n] = min(seg[2*n], seg[2*n+1]);
}
int sum(int s, int e, int n, int ns, int ne) {
prop(n,ns,ne);
if(e<=ns||ne<=s) return 1e9;
if(s<=ns&&ne<=e) return seg[n];
int mid = ns + ne >> 1;
return min(sum(s, e, 2*n, ns, mid), sum(s, e, 2*n+1, mid, ne));
}
};
int A[200005];
vector<int> V[200005];
vector<int> Query[200005];
signed main() {
cin.sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int N, K, R;
cin >> N >> K >> R;
int i, j;
for(i=0;i<N;i++) cin >> A[i];
for(i=0;i<N;i++) V[A[i]].push_back(i);
bool isPos = true;
for(i=0;i<R;i++) {
int B, Q;
cin >> B >> Q;
if(V[B].size() < Q) {
isPos = false;
continue;
}
int sz = V[B].size();
Query[0].push_back(V[B][Q-1]-1);
for(j=0;j<sz;j++) {
Query[V[B][j] + 1].push_back((j+Q < sz ? V[B][j+Q] - 1 : N));
}
}
if(!isPos) {
cout << "impossible";
return 0;
}
SegTree tree(N+5);
tree.cons();
int MAX = tree.MAX;
int ans = N;
for(i=0;i<N;i++) {
for(int n : Query[i]) {
tree.add(i, n+1, 1, 0, MAX/2);
//cout << "Add " << i << ' '<< n << '\n';
}
int res = tree.sum(i, N+1, 1, 0, MAX/2);
if(res < N) ans = min(ans, res - i + 1);
//cout<< i << " : " << res << '\n';
}
cout << ans;
}
