#include<algorithm>
#include<iostream>
#include<iomanip>
#include<cstring>
#include<numeric>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<stack>
#include<deque>
#include<cmath>
#include<map>
#include<set>
using namespace std;
#define ll long long
#define ld long double
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N, K, R; cin >> N >> K >> R;
vector<int> need(K), cnt(K), D(N+1);
for(int i = 1; i <= N; ++i){
cin >> D[i];
}
for(int i = 1; i <= R; ++i){
int B, Q; cin >> B >> Q;
need[B] = Q;
}
int done = 0;
for(int i = 0; i < K; ++i){
if(need[i] == 0)done++;
}
int l = 1, r, answer = 1e9;
for(r = 1; r <= N; ++r){
cnt[D[r]]++;
if(cnt[D[r]] == need[D[r]])done++;
while(l < r && cnt[D[l]] > need[D[l]]){
cnt[D[l++]]--;
}
if(done == K){
answer = min(answer, r - l + 1);
}
}
if(answer > N)cout << "impossible";
else cout << answer;
return 0;
}
