#include <bits/stdc++.h>
#define DIM 200010
#define INF 2000000000
using namespace std;
int aint[DIM*4],v[DIM],f[DIM];
deque <int> d[DIM];
int n,k,r,i,x,y;
void build (int nod, int st, int dr){
if (st == dr){
if (f[st])
aint[nod] = -INF;
else aint[nod] = INF;
return;
}
int mid = (st+dr)>>1;
build (nod<<1,st,mid);
build ((nod<<1)|1,mid+1,dr);
aint[nod] = min (aint[nod<<1],aint[(nod<<1)|1]);
}
void update (int nod, int st, int dr, int poz, int val){
if (st == dr){
aint[nod] = val;
return;
}
int mid = (st+dr)>>1;
if (poz <= mid)
update (nod<<1,st,mid,poz,val);
else update ((nod<<1)|1,mid+1,dr,poz,val);
aint[nod] = min (aint[nod<<1],aint[(nod<<1)|1]);
}
int main (){
//ifstream cin ("date.in");
//ofstream cout ("date.out");
cin>>n>>k>>r;
for (i=1;i<=n;i++){
cin>>v[i];
v[i]++;
}
for (i=1;i<=r;i++){
cin>>x>>y;
x++;
f[x] = y;
}
build (1,1,k);
int sol = INF;
for (i=1;i<=n;i++){
d[v[i]].push_back(i);
if (!f[v[i]])
continue;
if (d[v[i]].size() > f[v[i]])
d[v[i]].pop_front();
if (d[v[i]].size() == f[v[i]])
update (1,1,k,v[i],d[v[i]].front());
sol = min (sol,i - aint[1] + 1);
}
if (sol == INF)
cout<<"impossible";
else cout<<sol;
return 0;
}
