#include <bits/stdc++.h>
#pragma GCC optimize("Ofast", "unroll-loops")
using namespace std;
#define ll long long
#define int ll
#define FOR(i,a, b) for (int i=(a); i<(b); i++)
#define REP(i, n) FOR(i, 0, n)
#define REP1(i, n) FOR(i, 1, n+1)
#define pii pair<int, int>
#define SZ(x) (int)((x).size())
#define ALL(x) (x).begin(), (x).end()
#define f first
#define s second
#define pb push_back
const ll maxn = 2e5+5;
const ll inf = (1ll<<60);
signed main(){
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
int n, k, r; cin>>n>>k>>r;
vector<int> req(k), cur(k);
vector<int> vc(n);
REP(i, n){
cin>>vc[i];
}
REP(i, r){
int a, b; cin>>a>>b;
req[a]=b;
}
r=-1;
int cpos = 0;
REP(i, n){
cur[vc[i]]++;
while(cpos<k&&req[cpos]<=cur[cpos]){
cpos++;
}
if (cpos==k){
r=i;
break;
}
}
if (r==-1){
cout<<"impossible"<<endl;
return 0;
}
int ans=inf;
cpos=-1;
REP(i, n){
ans=min(ans, r-i+1);
cur[vc[i]]--;
if (cur[vc[i]]<req[vc[i]]){
cpos=vc[i];
r++;
while(r<n){
cur[vc[r]]++;
if (cur[cpos]>=req[cpos]){
break;
}
r++;
}
if (r==n){
break;
}
}
}
cout<<ans<<endl;
}
