#include<bits/stdc++.h>
#define endl "\n"
using namespace std ;
typedef long long ll;
typedef long double ld ;
#define pb push_back
#define pp pop_back
const int N=1e6+9;
const ll inf=1e18 ;
const ll mod = 1e9+9 ;
#define fast ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
ll n,k,q,cnt[N],freq[N],freq1[N],x[N],y[N],a[N],l,r;
map<ll,ll>mp1;
map<ll,ll>mp;
bool b=0;
int main()
{
fast;
ll ans=inf;
cin>>n>>k>>q;
for(int i=0; i<n; i++){
cin>>a[i];
}
set<ll>st;
for(ll i=0;i<q;i++){
cin>>x[i]>>y[i];
freq1[x[i]]+=y[i];
st.insert(x[i]);
}
for(ll i=0; i<n; i++){
freq[a[i]]++;
if(freq[a[i]]==freq1[a[i]])st.erase(a[i]);
while(freq[a[l]]>freq1[a[l]]) {
freq[a[l]]--;
l++;
}
if(st.empty())ans=min(ans,i-l);
}
if(ans==inf)cout<<"impossible";
else cout<<ans+1;
return 0;
}
