#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N = 300 + 4;
void fun () {
int n, k, m;
cin >> n >> m >> k;
vector<int> a(n + 1), b(m + 1);
for (int i = 1; i <= n; i++) cin >> a[i];
for (int i = 1; i <= m; i++) cin >> b[i];
if (k == 1) {
int s1 = 0;
for (int i = 1; i <= m; i++) s1 += b[i];
vector<int> dp(s1 + 1);
dp[0] = 1;
for (int i = 1; i <= m; i++) {
for (int j = s1; j >= b[i]; j--) {
dp[j] |= dp[j - b[i]];
}
}
int s = 0;
for (int i = 1; i <= n; i++) {
s += a[i];
}
if (s1 < s) {
cout << "Impossible";
return;
}
for (int i = s; i <= s1; i++) {
if (dp[i]) {
cout << i - s;
return;
}
}
}
int ans = 1e18, s = 0;
for (int i = 1; i <= n; i++) s += a[i];
for (int i = 1; i <= n; i++) {
if (a[i] < k) {
cout << "Impossible";
return;
}
}
for (int mask = 0; mask < (1 << m); mask++) {
if (__builtin_popcount(mask) < k) continue;
int s1 = 0;
int res = k;
vector<int> vt;
for (int i = 0; i < m; i++) {
if (mask >> i & 1) {
s1 += b[i + 1];
if (b[i + 1] >= n) {
res--;
}
else {
vt.push_back(b[i + 1]);
}
}
}
if (s1 < s) continue;
sort(vt.rbegin(), vt.rend());
int now = 0;
for (auto e : vt) now += e;
res -= now / n;
if (res <= 0) {
ans = min(ans, s1 - s);
}
}
if (ans == 1e18) cout << "Impossible";
else cout << ans << endl;
}
signed main () {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int tt = 1;
//cin >> tt;
while (tt--) fun();
return 0;
}
