#include <bits//stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<long long, null_type, less<long long>, rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag,
tree_order_statistics_node_update>
ordered_multiset;
#define ll long long
#define iloop(m, h) for (auto i = m; i != h; i += (m < h ? 1 : -1))
#define jloop(m, h) for (auto j = m; j != h; j += (m < h ? 1 : -1))
#define kloop(m, h) for (auto k = m; k != h; k += (m < h ? 1 : -1))
#define lloop(m, h) for (auto l = m; l != h; l += (m < h ? 1 : -1))
#define pll pair<ll, ll>
#define INF 1000000000000000
#define MOD1 1000000007
#define MOD2 998244353
#define MOD3 1000000009
ll n, m, t, t1, t2, f;
ll a[200005], req[200005], cc[200005];
ll lb, ub, mid;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m >> t;
iloop(0, n) cin >> a[i];
iloop(0, m) req[i] = 0;
iloop(0, t) {
cin >> t1 >> t2;
req[t1] = max(req[t1], t2);
}
lb = 1, ub = n+1;
while (lb < ub) {
mid = (lb + ub) >> 1;
iloop(0, m) cc[i] = 0;
f = 0;
iloop(0, n) {
cc[a[i]]++;
if (cc[a[i]] == req[a[i]]) f++;
if (i >= mid) {
if (cc[a[i-mid]] == req[a[i-mid]]) f--;
cc[a[i-mid]]--;
}
if (f == t) break;
}
if (f == t) ub = mid;
else lb = mid + 1;
}
if (lb == n+1) cout << "impossible";
else cout << lb;
}
