#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 303;
const int K = 90000;
int a[N];
bitset<N* N> dp1;
int dp2[N * N];
int main() {
cin.tie(nullptr)->sync_with_stdio(false);
memset(dp2, 0xc0, sizeof dp2);
int n, m, k;
cin >> n >> m >> k;
int sum = 0;
for (int i = 1;i <= n;i++) cin >> a[i], sum += a[i];
for (int i = 1;i <= n;i++) {
if (a[i] < k) {
cout << "Impossible\n";
return 0;
}
}
dp1[0] = 1;
dp2[0] = 0;
for (int i = 1;i <= m;i++) {
int b;
cin >> b;
if (b < n) {
dp1 |= (dp1 << b);
}
else {
for (int j = K;j >= b;j--) dp2[j] = max(dp2[j], dp2[j - b] + 1);
}
}
vector<int> can;
for (int i = 0;i <= K;i++) {
if (dp1[i]) can.push_back(i);
}
int mn = 1e9;
for (int i = 0;i <= K;i++) {
if (dp2[i] < 0) continue;
int need = max(sum - i, (k - dp2[i]) * n);
if (can.back() < need) continue;
mn = min(mn, *lower_bound(can.begin(), can.end(), need) + i);
}
if (mn == 1e9) cout << "Impossible\n";
else cout << mn - sum << '\n';
return 0;
}
