#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e10;
vector <ll> T;
ll k = 1;
void build(vector <ll> a){
ll n = a.size();
while (k < n)k *= 2;
T.resize(2*k);
for (int i = 0; i < n; i++)T[i+k] = a[i];
for (int i = n; i < k; i++)T[i+k] = INF;
for (int i = k-1; i > 0; i--)T[i] = min(T[2*i], T[2*i+1]);
}
void reset(vector <ll> a){
ll n = a.size();
for (int i = 0; i < n; i++)T[i+k] = a[i];
for (int i = n; i < k; i++)T[i+k] = INF;
for (int i = k-1; i > 0; i--)T[i] = min(T[2*i], T[2*i+1]);
}
void update(ll x, ll v){
x += k; T[x] += v; x >>= 1;
for (; x; x >>= 1){
T[x] = min(T[2*x], T[2*x+1]);
}
}
int main(){
ll n, K, r; cin >> n >> K >> r;
vector <ll> v(n), aa(K, 0);
for (int i = 0; i < n; i++)cin >> v[i];
for (int i = 0; i < r; i++){
ll a, b; cin >> a >> b;
aa[a] = -b;
}
build(aa);
ll s = 1, e = n+1, m, M = -1;
while (e > s){
m = (e+s)/2;
for (int i = 0; i < m; i++)update(v[i], 1);
for (int i = m; i < n; i++){
if (T[1] >= 0){M = m; break;}
update(v[i-m], -1); update(v[i], 1);
}
if (T[1] >= 0)M = m;
if (M == m)e = m;
else s = m+1;
reset(aa);
}
if (M == -1)cout << "impossible";
else cout << M;
}
