#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, k, r;
cin >> n >> k >> r;
int a[n];
for (int i = 0; i < n; i++)
cin >> a[i];
int q[k] = {};
for (int i = 0; i < r; i++) {
int b, c;
cin >> b >> c;
q[b] = c;
}
set<pair<int, int>> st;
for (int i = 0; i < k; i++) {
if (q[i])
st.insert({-1, i});
}
vector<vector<int>> p(k);
auto get = [&](int d) {
return ((int)p[d].size() < q[d] ? -1 : p[d][(int)p[d].size() - q[d]]);
};
int res = n + 1;
for (int i = 0; i < n; i++) {
if (q[a[i]]) {
assert(st.count({get(a[i]), a[i]}));
st.erase({get(a[i]), a[i]});
}
p[a[i]].push_back(i);
if (q[a[i]]) {
st.insert({get(a[i]), a[i]});
}
if (st.begin()->first != -1)
res = min(res, i - st.begin()->first + 1);
}
if (res == n + 1) {
cout << "impossible\n";
return 0;
}
cout << res << '\n';
return 0;
}
