#include<bits/stdc++.h>
using namespace std;
#ifdef ONPC
#include"debug.h"
#else
#define debug(...) 42
#endif
#define endl '\n'
#define ll long long
#define pii pair<int,int>
#define F first
#define S second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
const int mod = 1e9 + 7;
const int MAXN = 1e6 + 15;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, k, r;
cin >> n >> k >> r;
vector<int> a(n), frq(k), needs(k);
for (int i = 0; i < n; i++){
cin >> a[i];
}
set<int> active;
for (int i = 0; i < r; i++){
int u, v;
cin >> u >> v;
needs[u] = v;
active.insert(u);
}
int p1 = 0, p2 = 0;
int ans = inf;
while (p1 < n){
while (p2 < n && sz(active)){
frq[a[p2]]++;
if (frq[a[p2]] == needs[a[p2]]) active.erase(a[p2]);
p2++;
}
if (sz(active) == 0){
ckmin(ans, p2 - p1);
}
if (frq[a[p1]] == needs[a[p1]]){
active.insert(a[p1]);
}
frq[a[p1]]--;
p1++;
}
if (ans != inf)
cout << ans << endl;
else
cout << "impossible\n";
}
