#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define x first
#define y second
#define pb push_back
#define mp make_pair
#define all(v) v.begin(),v.end()
#define sz(v) (int)v.size()
#define up_b upper_bound
#define low_b lower_bound
#define nl '\n'
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;
const int N=2e5+500;
const int M=1e6+1;
const ll inf=2e9+11;
const ld EPS=1e-6;
const int INF=1e9;
const ll mod=998244353/*1e9+7*/;
const int dx[4]={1,0,0,-1};
const int dy[4]={0,1,-1,0};
int a[N],b[N],c[N];
void solve(){
int n,k,m;
cin>>n>>k>>m;
for(int i=1;i<=n;i++){
cin>>a[i];
}
for(int i=0;i<k;i++){
b[i]=-inf;
}
for(int i=1;i<=m;i++){
int x,y;
cin>>x>>y;
b[x]=y;
}
int l=1;
int cnt=0;
int ans=inf;
for(int r=1;r<=n;r++){
c[a[r]]++;
if(c[a[r]]==b[a[r]])cnt++;
while(c[a[l]]>b[a[l]]){
c[a[l]]--;
l++;
}
if(cnt==m)ans=min(ans,r-l+1);
}
if(ans==inf)cout<<"impossible";
else cout<<ans;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0),cout.tie(0);
int T=1;
//cin>>T;
for(int i=1;i<=T;i++){
solve();
cout<<nl;
}
return 0;
}
