#include <bits/stdc++.h>
#define fr(i, n, m) for(int i = (n); i < (m); i ++)
#define pb push_back
#define st first
#define nd second
#define pq priority_queue
#define all(x) begin(x), end(x)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pii;
const ll inf = 1e18;
const int i_inf = 1e9;
const ll mod = 1e9+7;
mt19937 _rand(time(NULL));
const int mxn = 2e5;
int n, k, r;
int a[mxn];
int c[mxn];
int cnt[mxn];
void solve(){
cin >> n >> k >> r;
fr(i, 0, n){
cin >> a[i];
}
fr(i, 0, r){
int nuc;
cin >> nuc >> c[nuc];
}
int in = 0;
int p = 0;
while(in < r && p < n){
cnt[a[p]] ++;
if(cnt[a[p]] == c[a[p]]){
++in;
}
++p;
}
if(in < r){
cout<<"impossible"<<endl;
return;
}
--p;
int ans = p+1;
int l = 0;
while(p < n){
while(l < p && cnt[a[l]] > c[a[l]]){
cnt[a[l]]--;
++l;
}
ans = min(ans, p-l+1);
++p;
if(p < n){
cnt[a[p]]++;
}
}
cout<<ans<<endl;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
solve();
}
