#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (int i = a; i < b; ++i)
#define per(i, a, b) for (int i = b - 1; i >= a; --i)
#define trax(a, x) for (auto& a : x)
#define sz(a) a.size()
typedef pair<int, int> ii;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;
int main() {
cin.tie(0)->sync_with_stdio(0);
int n, k, r, quant[200001], dna[200001];
memset(quant, 0, sizeof(quant));
cin >> n >> k >> r;
rep(i, 0, n) cin >> dna[i];
rep(i, 0, r) {
int b, q;
cin >> b >> q;
quant[b] = q;
}
int lo = 1, hi = n+1;
vi curr,dummy(n,0);
while (lo < hi) {
int mid = (hi + lo) >> 1,have=0;
curr=dummy;
bool work=0;
rep(i, 0, mid - 1){
int base=dna[i];
if(++curr[base]==quant[base])++have;
}
rep(i,mid-1,n){
int base=dna[i];
++curr[base];
if(curr[base]==quant[base])++have;
if(have==r){
work=1;
break;
}
base=dna[i-mid+1];
if(quant[base]==curr[base])--have;
--curr[base];
}
if(work)hi=mid;
else lo=mid+1;
}
if(n<lo)cout<<"impossible"<<endl;
else cout<<lo<<endl;
}
