#include <bits/stdc++.h>
#define sz(x) (int)x.size()
#define vec vector
#define pb push_back
#define rall(x) x.rbegin(),x.rend()
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define f first
#define s second
using namespace std;
typedef unsigned long long ull;
auto rnd=bind(uniform_int_distribution<long long>(1,1e18),mt19937(time(0)));
signed main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
int n,k,q;
cin>>n>>k>>q;
vec<pii>need(q);
vec<int>a(n);
map<int,int>mp;
int cr=0;
for(int i=0;i<n;i++){
cin>>a[i];
if(!mp.count(a[i])){
mp[a[i]]=cr++;
}
a[i]=mp[a[i]];
}
for(auto &z : need){
cin>>z.f>>z.s;
if(!mp.count(z.f)) mp[z.f]=cr++;
z.f=mp[z.f];
}
vec<int>pos(n,-1);
vec<vec<int>>vc(cr,vec<int>());
vec<int>last(sz(mp),-1);
vec<int>nxt(cr,-1);
for(auto &z : need) nxt[z.f]=z.s;
for(int i=0;i<n;i++){
pos[i]=sz(vc[a[i]]);
vc[a[i]].pb(i);
}
for(auto &z : vc) reverse(all(z));
int ans=2e9;
int mx=-1;
for(auto &z : need){
if(sz(vc[z.f])<z.s){
cout<<"impossible";
return 0;
}
mx=max(mx,vc[z.f][sz(vc[z.f])-z.s]);
}
ans=min(ans,mx+1);
for(int i=0;i<n;i++){
int clr=a[i];
vc[clr].pop_back();
if(nxt[clr]!=-1){
if(sz(vc[clr])<nxt[clr]) break;
mx=max(mx,vc[clr][sz(vc[clr])-nxt[clr]]);
}
ans=min(ans,mx-i);
// cerr<<i<<' '<<mx<<endl;
}
if(ans==2e9) cout<<"impossible";
else cout<<ans;
return 0;
}
