#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define show(x,y) cout << y << " " << #x << endl;
#define show2(x,y,i,j) cout << y << " " << #x << " " << j << " " << #i << endl;
#define show3(x,y,i,j,p,q) cout << y << " " << #x << " " << j << " " << #i << " " << q << " " << #p << endl;
#define show4(x,y) for(auto it:x) cout << it << " "; cout << #y << endl;
typedef pair<int,int>pii;
typedef pair<pii,int>pi2;
void solve(){
int n,k,r;
cin >> n >> k >> r;
int arr[n];
for(int x=0;x<n;x++){
cin >> arr[x];
}
int need[n];
memset(need,-1,sizeof(need));
int temp,temp2;
for(int x=0;x<r;x++){
cin >> temp >> temp2;
need[temp]=temp2;
}
int l=0;
int done=0;
int cnt[n];
memset(cnt,0,sizeof(cnt));
int best=LONG_LONG_MAX;
for(int x=0;x<n;x++){
//include x
int val=arr[x];
cnt[val]++;
if(cnt[val]==need[val]) done++;
while(done==r){
best=min(best,x-l+1);
int cur=arr[l];
if(cnt[cur]==need[cur]) done--;
cnt[cur]--;
l++;
}
}
if(best==LONG_LONG_MAX){
cout << "impossible\n";
}
else cout << best;
}
int32_t main(){
ios::sync_with_stdio(0);
cin.tie(0);
int t=1;
//cin >> t;
while(t--){
solve();
}
}
