#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vt vector
#define ar array
int neededAmounts[200005];
int totalAmounts[200005];
int curAmount[200005];
bool needed [200005];
int totalNucles = 0;
int n;
void solve(){
int k, r;
cin >> n >> k >> r;
vt<int> nucles (n);
for(int i = 0; i < n; i++){
cin >> nucles[i];
totalAmounts[nucles[i]]++;
}
for(int i = 0; i < r; i++){
int a, b;
cin >> a >> b;
if (totalAmounts[a] < b){
cout << "impossible" << endl;
return;
}
neededAmounts[a] = b;
totalNucles += b;
needed[a] = true;
}
int left = 0;
int right = -1;
int res = n;
while (r > 0){
if (curAmount[nucles[right + 1]] + 1 == neededAmounts[nucles[right + 1]]){
curAmount[nucles[right + 1]]++;
r--;
right++;
}else{
curAmount[nucles[right + 1]]++;
right++;
}
}
res = right - left + 1;
while (right < n){
if (curAmount[nucles[left]] > neededAmounts[nucles[left]]){
curAmount[nucles[left]]--;
left++;
res = min(res, right - left + 1);
continue;
}
curAmount[nucles[right + 1]]++;
right++;
}
cout << res << endl;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
int testcases = 1;
// cin >> testcases;
while(testcases--){
solve();
}
return 0;
}
