#pragma GCC optimize("O1,O2,O3,Ofast,unroll-loops")
#include <bits/stdc++.h>
#include <string>
#include <iostream>
#include <cmath>
#include <numeric>
#include <stack>
#include <queue>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<vector<int>> vvi;
typedef vector<vector<pi>> vvpi;
typedef vector<ld> vd;
typedef vector<long long> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
#define FOR(i, a, b) for (int i = a; i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= a; i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)
#define uid(a, b) uniform_int_distribution<int>(a, b)(rng)
#define len(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define F first
#define nl endl
#define S second
#define lb lower_bound
#define ub upper_bound
#define aint(x) x.begin(), x.end()
#define raint(x) x.rbegin(), x.rend()
#define ins insert
const int M = 1e9+7;
void init(string name)
{
freopen((name + ".in").c_str(), "r", stdin);
freopen((name + ".out").c_str(), "w", stdout);
}
void fastIO()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
}
int n,r,k;
void solve()
{
cin >> n >> k >> r;
vi arr(n);
FOR(i,0,n)cin >> arr[i];
vi needed(k,0);
int counter = 0;
FOR(i,0,r){
int a,b;cin >> a >> b;
if(b == 0)counter ++;
needed[a] = b;
}
r = r-counter;
if(r == 0){
cout << 0 << endl;
return;
}
int ans = n+1;
int s = 0,e = 0,cnt = 0;
vi tmp = needed;
while(e < n){
while(cnt < r && e < n){
if(needed[arr[e]] > 0){
tmp[arr[e]] --;
if(tmp[arr[e]] == 0){
cnt ++;
}
}
e++;
}
while(cnt == r && s < e){
ans = min(ans,e-s);
if(needed[arr[s]] > 0){
tmp[arr[s]] ++;
if(tmp[arr[s]] == 1){
cnt --;
}
}
s++;
}
}
if(ans != n+1){
cout << ans << endl;
return;
}
cout << "impossible" << endl;
}
int main()
{
fastIO();
// init("test");
int t = 1;
// cin >> t;
while (t--)
solve();
return 0;
}
