#include <bits/stdc++.h>
using namespace std;
const int N = 302;
const int inf = 1000 * 1000 * 1000;
template<typename T>
istream& operator >> (istream& is, vector<T> &a) { for(T &element : a) is >> element; return is; }
signed main() {
std::ios::sync_with_stdio(0);
std::cin.tie(0);
std::cout.tie(0);
#ifdef saarang
freopen("/home/saarang/Documents/cp/input.txt", "r", stdin);
freopen("/home/saarang/Documents/cp/output.txt", "w", stdout);
#endif
int n, m, k;
cin >> n >> m >> k;
vector<int> a(n), b(m);
cin >> a; cin >> b;
if(*min_element(a.begin(), a.end()) < k)
return cout << "Impossible" << '\n', 0;
vector<int> dp(N * N, -1);
dp[0] = 0;
for(int i = 0; i < m; i++) {
for(int j = m * N - b[i]; j >= 0; j--)
if(dp[j] != -1)
dp[j + b[i]] = max(dp[j + b[i]], dp[j] + min(b[i], n));
}
int answer = inf;
int sum = accumulate(a.begin(), a.end(), 0);
for(int i = sum; i < N * N; i++)
if(dp[i] >= n * k)
answer = min(answer, i - sum);
cout << (answer ^ inf ? to_string(answer) : "Impossible") << '\n';
}
