#include <iostream>
#include <math.h>
#include <vector>
#include <string>
#include <algorithm>
#include <queue>
#include <stack>
#include <map>
#include <cstring>
#include <iomanip>
#include <set>
#include <bitset>
#include <unordered_map>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using piii = tuple<int,int,int>;
#define f first
#define s second
#define endl '\n'
#define all(x) begin(x),end(x)
#define m_p make_pair
int main(){
int n;cin >> n;
int k;cin >> k;
int r;cin >> r;
vector<int> vc;
vector<int> need(k,0);
vector<vector<int>> color(k);
vector<queue<int>> next(k);
for(int i{};i < n;i++){
int g;cin >> g;
vc.emplace_back(g);
color[g].emplace_back(i);
}
int ans = n;
int cur = 0;
for(int i{};i < r;i++){
int a,b;cin >> a >> b;
need[a] = b;
if(b > color[a].size()){
cout << "impossible";
return 0;
}
for(int j{};j+b-1 < color[a].size();j++){
next[a].emplace(color[a][j+b-1]);
}
cur = max(cur,next[a].front());
}
for(int i{};i < n;i++){
cur = max(cur,i+1);
if(need[vc[i]]){
next[vc[i]].pop();
if(next[vc[i]].empty()) break;
cur = max(cur,next[vc[i]].front());
}
ans = min(ans,cur-i);
}
cout << ans;
}
