#include <bits/stdc++.h>
using namespace std;
#define mid (l + ((r - l) / 2))
#define pb push_back
#define F first
#define S second
int64_t mod = 998244353 ;
void solve(int64_t tt)
{
int64_t n, m, k, x = -1, y = 0, z = 1, ans = 1e18, sum = 0, p = 1, cnt = 0, cnt0 = 0, cnt1 = 0, mx = -1, mn = 1e18 ;
string s, t = "" ;
bool ok = 1 ;
cin >> n >> m >> k ;
vector<int64_t> a(n + 1), b(k + 1), c(k + 1) ;
for(int64_t i = 1 ; i <= n ; i++) cin >> a[i] ;
/*c[0]++,*/ cnt = k ;
for(int64_t i = 1 ; i <= k ; i++)
{
cin >> x >> y ;
b[x] = y ;
}
for(int64_t i = 0 ; i <= n ; i++)
{
if(i) c[a[i]]-- ;
if(i && c[a[i]] == b[a[i]] - 1) cnt++ ;
while(p <= n && cnt > 0)
{
if(c[a[p]] + 1 == b[a[p]]) cnt-- ;
c[a[p]]++, p++ ;
}
//cout << i << ' ' << p << ' ' << cnt << endl;
if(!cnt) ans = min(ans , p - i - 1) ;
}
if(ans == 1e18) cout << "impossible" << endl;
else cout << ans << endl;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
/*freopen("defining_prizes_validation_input.txt", "r", stdin);
freopen("BVout.txt", "w", stdout);*/
int tt = 1 ;
//cin >> tt ;
for(int64_t i = 1 ; i <= tt ; i++) solve(i) ;
}
/*
* empty space to be able to see the last part of the code ;)
*
* some advices :
* https://codeforces.com/blog/entry/146051
* https://codeforces.com/blog/entry/22616
* do not eat penaltieeeeeeeeeeeeeeeeeeeeeeeeeeeees in official contests you are the last of people who solved like you, you are so ugly
* do not forget to zero your global arrays in test cases
* check the limits of your code
* test edge cases (the least n , the biggest n if you can , etc...)
* run time error may happened because of exceed the limits (but it may happen when you devide or "'mod'" by zero)
* writing....
* ...
* ..
* .
*/
