#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt,tune=native")
#define fio ios_base::sync_with_stdio(0);cin.tie(0);
#define ll long long
#define ld long double
#define en exit(0);
#define pb push_back
#define fi first
#define se second
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int N = 2e5 + 5;
const int INF = 1e9 + 5;
vector<int> pos[N], ops[N];
int main()
{
fio
// ifstream cin("in.in");
int n, k, r;
cin >> n >> k >> r;
int a[n + 1];
for(int i = 0;i < k;i++)
pos[i].pb(0);
for(int i = 1;i <= n;i++)
{
cin >> a[i];
pos[a[i]].pb(i);
}
int to = n;
while(r--)
{
int val, mn;
cin >> val >> mn;
vector<int> &ve = pos[val];
int sz = ve.size();
if(sz - 1 < mn)
return cout << "impossible", 0;
for(int i = mn;i < sz;i++)
{
int l = ve[i - mn] + 1, r = ve[i - mn + 1];
int x = ve[i];
ops[l].pb(x);
ops[r + 1].pb(-x);
}
to = min(to, ve[sz - mn]);
}
int res = INF;
multiset<int> s;
for(int i = 1;i <= to;i++)
{
for(auto x:ops[i])
{
if(x > 0)
s.insert(x);
else
s.erase(s.find(-x));
}
assert(!s.empty());
int r = *s.rbegin();
res = min(res, r - i + 1);
}
cout << res;
return 0;
}
