// Starcraft 2 enjoyer //
#include <bits/stdc++.h>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
#define LSOne(X) ((X) & -(X))
const int N = 2e5 + 5;
const int M = 1 << 5;
const int K = 19;
const int LG = 20;
const long long INF = 3e18;
const int C = 26;
const int B = 1000;
const int MOD = 1e9 + 7;
int n, k, q, a[N], cnt[N], need[N], ans, l, r, bad;
inline void solve()
{
cin >> n >> k >> q;
memset(need, -1, sizeof(need));
bad = 0;
for (int x = 1; x <= n; x++)
{
cin >> a[x];
}
ans = n + 1;
for (int x = 0; x < q; x++)
{
int a, b;
cin >> a >> b;
need[a] = b;
}
bad = q;
l = 1, r = 1;
while (r <= n)
{
cnt[a[r]]++;
if (need[a[r]] == cnt[a[r]])
{
bad--;
}
while (!bad)
{
ans = min(ans, r - l + 1);
cnt[a[l]]--;
if (need[a[l]] > cnt[a[l]])
bad++;
l++;
}
r++;
}
if(ans == n + 1) cout << "impossible";
else cout << ans;
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
for (int x = 1; x <= t; x++)
{
solve();
}
return 0;
}
