#pragma GCC optimize("-O3")
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define vl vector<ll>
#define vi vector<int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pb push_back
#define p_b pop_back
#define f first
#define s second
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
void solve()
{
ll n, k, r, i;
cin >> n >> k >> r;
ll ans = LLONG_MAX;
map<ll, ll>mp, mp2;
vl v(n+5);
for(i = 1; i <= n; i++)
cin >> v[i];
for(i = 0; i < r; i++)
{
ll b, q;
cin >> b >> q;
mp[b] = q;
}
ll f = n - r, j = 1;
for(i = 1; i <= n; i++)
{
mp2[v[i]]++;
if(mp2[v[i]] == mp[v[i]])
f++;
if(f < n)
continue;
while(mp2[v[j]] != mp[v[j]])
{
mp2[v[j]]--;
j++;
}
ans = min(ans, i - j + 1);
}
if(ans == LLONG_MAX)
cout << "impossible\n";
else
cout << ans << "\n";
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll tests = 1;
//cin >> tests;
while(tests--)
{
solve();
}
}
