#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pld pair<ld, ld>
#define pb push_back
#define fi first
#define se second
#define debug(x) cout << #x << " => " << x << endl
#define all(x) x.begin(),x.end()
int main()
{
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
int n,k,R;cin>>n>>k>>R;
int a[n];
for(int i=0;i<n;i++) cin>>a[i];
int need[k],cnt[k];
memset(need,0,sizeof(need));
memset(cnt,0,sizeof(cnt));
for(int i=0;i<R;i++)
{
int b,q;cin>>b>>q;
need[b]=q;
}
int l=0,r=0,cntOK=0,ans=1e9;
while(r<n)
{
cnt[a[r]]++;
if(cnt[a[r]]==need[a[r]]) cntOK++;
r++;
while(cntOK==R)
{
ans=min(ans,r-l);
cnt[a[l]]--;
if(cnt[a[l]]==need[a[l]]-1) cntOK--;
l++;
}
}
if(ans==1e9) cout<<"impossible";
else cout<<ans;
return 0;
}
