#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for (int i = (a); i <= (b); i++)
#define repa(i,a,b) for (int i = (a); i >= (b); i--)
#define lli long long int
#define debug(a) cout << #a << " = " << a << endl
#define debugsl(a) cout << #a << " = " << a << ", "
#define MAX 200000
lli n,r,k,a,b,ini,falt,res;
lli arr[MAX+2], requeridos[MAX+2];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> k >> r;
rep(i,1,n) cin >> arr[i];
rep(i,1,r) {
cin >> a >> b;
requeridos[a] = b;
falt += b;
}
ini = 1;
res = -1;
rep(fin,1,n) {
a = arr[fin];
if(requeridos[a] > 0) falt--;
requeridos[a]--;
while (falt == 0) {
a = fin-ini+1;
if (res == -1 || a < res) res = a;
a = arr[ini++];
if (requeridos[a] >= 0) falt++;
requeridos[a]++;
}
}
if (res == -1) cout << "impossible";
else cout << res;
}
