#include <bits/stdc++.h>
using namespace std;
#define INF (int)1e9
#define f first
#define s second
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
void Solve()
{
int n, m, k; cin >> n >> m >> k;
vector <int> a(n), b(m);
int sum = 0;
for (auto &x : a) {
cin >> x;
sum += x;
if (x < k){
cout << "Impossible\n";
return;
}
}
for (auto &x : b) cin >> x;
vector <int> dp(m * 300 + 1, -INF);
dp[0] = 0;
int cnt = 0;
for (auto x : b){
cnt += 300;
for (int i = cnt; i >= x; i--){
dp[i] = max(dp[i], dp[i - x] + min(x, n));
}
}
for (int i = sum; i <= m * 300; i++){
if (dp[i] >= k * n){
cout << i - sum << "\n";
return;
}
}
cout << "Impossible\n";
}
int32_t main()
{
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// freopen("in", "r", stdin);
// freopen("out", "w", stdout);
// cin >> t;
for(int i = 1; i <= t; i++)
{
//cout << "Case #" << i << ": ";
Solve();
}
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
return 0;
}
