#include <algorithm>
#include <bitset>
#include <cstdint>
#include <cstring>
#include <iostream>
#include <limits.h>
#include <math.h>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <chrono>
//#define int long long
#define loop(X, N) for(int X = 0; X < (N); X++)
#define all(V) V.begin(), V.end()
#define rall(V) V.rbegin(), V.rend()
using namespace std;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
int main() {
int n, k, r;
cin >> n >> k >> r;
vi dna(n);
loop(i, n)
cin >> dna[i];
vi requirements(k);
loop(i, r) {
int b, q;
cin >> b >> q;
requirements[b] = q;
}
int best = INT_MAX;
int rPtr = 0;
int reqSat = 0;
vi freq(k);
loop(i, n) {
while (rPtr < n && reqSat < r) {
int base = dna[rPtr];
freq[base]++;
if (requirements[base] == freq[base])
reqSat++;
rPtr++;
}
if (reqSat == r)
best = min(best, rPtr - i);
int base = dna[i];
if (requirements[base] == freq[base])
reqSat--;
freq[base]--;
}
if (best == INT_MAX)
cout << "impossible" << endl;
else
cout << best << endl;
return 0;
}
