#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 5;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, m, k;
cin >> n >> m >> k;
vector<int> a(n), b(m);
for(int& i : a) {
cin >> i;
}
for(int& i : b) {
cin >> i;
}
int time = accumulate(a.begin(), a.end(), 0);
int ans = INF;
for(int mask = 0; mask < (1 << m); mask++) {
vector<int> chefs;
if (__builtin_popcount(mask) < k) continue;
for(int i = 0; i < m; i++) {
if (mask & (1 << i)) {
chefs.push_back(b[i]);
}
}
int sum = accumulate(chefs.begin(), chefs.end(), 0);
if (sum < time || ans < sum-time) continue;
bool ok = true;
for(int i = 0; i < n && ok; i++) {
if (a[i] < k) {
ok = false;
break;
}
sort(chefs.rbegin(), chefs.rend());
for(int j = 0; j < k; j++) {
if (chefs[j] <= 0) {
ok = false;
break;
}
chefs[j]--;
}
}
if (ok) {
ans = sum-time;
}
}
if (ans == INF) {
cout << "Impossible\n";
} else {
cout << ans << "\n";
}
return 0;
}
