#include <bits/stdc++.h>
#pragma GCC optimize ("O2,unroll-loops")
//#pragma GCC optimize("no-stack-protector,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr<<#x<<'='<<(x)<<endl;
#define debugp(x) cerr<<#x<<"= {"<<(x.first)<<", "<<(x.second)<<"}"<<endl;
#define debug2(x, y) cerr<<"{"<<#x<<", "<<#y<<"} = {"<<(x)<<", "<<(y)<<"}"<<endl;
#define debugv(v) {cerr<<#v<<" : ";for (auto x:v) cerr<<x<<' ';cerr<<endl;}
#define all(x) x.begin(), x.end()
#define pb push_back
#define kill(x) return cout<<x<<'\n', 0;
const int inf=1000000010;
const ll INF=10000000000000010LL;
const int mod=1000000007;
const int MAXN=300010, LOG=20;
int n, m, k, u, v, x, y, t, a, b, ans;
int A[MAXN], ted[MAXN];
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
cin>>n>>k>>m;
for (int i=1; i<=n; i++) cin>>A[i];
for (int i=0; i<m; i++) cin>>x>>y, ted[x]+=y;
int j=1, i=1;
while(i<=n){
m-=(0==--ted[A[i]]);
if (!m) break ;
i++;
}
if (m) kill("impossible")
while (ted[A[j]]) ted[A[j++]]++;
ans=i-j+1;
for (i++; i<=n; i++){
ted[A[i]]--;
while (ted[A[j]]) ted[A[j++]]++;
ans=min(ans, i-j+1);
}
kill(ans)
return 0;
}
