#include <bits/stdc++.h>
#define boost ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define int long long
using namespace std;
const int inf=1e17;
const int N=2e5+5;
const int N1=1e5+5;
const int N2=5e6+6;
const int mod=1e9+7;
const int k1=447;
struct edge{
int d,in;
};
struct edge1{
int l,r;
};
vector<int>v;
int dp[N];
int dp1[N];
vector<int>v1;
int dp2[N];
signed main(){
boost;
int n,k,q;
cin>>n>>k>>q;
v.push_back(0);
for(int i=1;i<=n;i++){
int x;
cin>>x;
dp[x]++;
v.push_back(x);
}
int ok2=0;
int cnt1=0;
for(int i=1;i<=q;i++){
int x,cnt;
cin>>x>>cnt;
dp1[x]=cnt;
dp2[x]=1;
cnt1++;
if(dp[x]<cnt){
ok2=1;
}
}
if(ok2==1){
cout<<"impossible";
return 0;
}
for(int i=1;i<=n;i++){
dp[v[i]]=0;
}
int l=1;
int ans=n;
for(int r=1;r<=n;r++){
dp[v[r]]++;
if(dp[v[r]]>=dp1[v[r]]&&dp1[v[r]]!=0&&dp2[v[r]]==1){
cnt1--;
dp2[v[r]]=0;
}
int ok3=0;
if(cnt1==0){
ok3=1;
}
while(cnt1==0&&l<=r){
dp[v[l]]--;
if(dp[v[l]]<dp1[v[l]]&&dp1[v[l]]!=0){
cnt1++;
dp2[v[l]]=1;
}
l++;
}
if(ok3==1){
ans=min(ans,r-(l-1)+1);
}
}
cout<<ans;
}
