#include <iostream>
#include <vector>
using namespace std;
bool dp[601][601];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, m, k;
cin >> n >> m >> k;
vector<int> a(n);
int total_work = 0;
for (int& x : a) {
cin >> x;
total_work += x;
if (x < k) {
cout << "Impossible\n";
return 0;
}
}
int const difference_work = n * k;
vector<int> b(m);
for (int& x : b)
cin >> x;
dp[0][0] = true;
for (int const& chef : b) {
int const delta_d = min(chef, n);
int const delta_t = chef;
for (int d = 600; d >= delta_d; d--) {
for (int t = 600; t >= delta_t; t--) {
dp[d][t] |= dp[d - delta_d][t - delta_t];
// if (dp[d][t]) {
// cout << "dp[" << d << "][" << t << "] possible!\n";
// }
}
}
}
for (int t = total_work; t <= 600; t++) {
for (int d = difference_work; d <= 600; d++) {
if (dp[d][t]) {
cout << t - total_work << "\n";
return 0;
}
}
}
cout << "Impossible\n";
}
