#include<bits/stdc++.h>
#define ll long long
#define pb push_back
#define F first
#define S second
#define coy cout<<"YES\n"
#define con cout<<"NO\n"
#define co1 cout<<"-1\n"
#define sc(x) scanf("%lld",&x)
#define all(x) x.begin(),x.end()
#define fast ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
const int SI=3e5+7;
ll INF=8e18+7;
int dx[] = {1 , -1 , 0 , 0};
int dy[] = {0 , 0 , 1 , -1};
int MOD=1e9+7;
ll n,k,r;
ll a[SI],w[SI],c[SI];
ll st;
int main()
{
fast
cin>>n>>k>>r;
for (int i=0;i<n;i++)
cin>>a[i];
for (int i=0;i<r;i++)
{
ll x,y;
cin>>x>>y;
w[x]=y;
st++;
}
ll f=0,s=0,ans=INF;
while (f<n)
{
while (s<n&&st)
{
c[a[s]]++;
if (c[a[s]]==w[a[s]])
st--;
s++;
}
//cout<<f<<" "<<s<<"\n";
if (s==n)
break;
ans=min(ans,s-f);
if (c[a[f]]==w[a[f]])
st++;
c[a[f++]]--;
}
if (ans==INF)
cout <<"impossible";
else cout <<ans;
// use scanf not cin
return 0;
}
/*
5 2 2
0 1 1 0 1
0 1
1 1
*/
