#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define F first
#define S second
#define pb push_back
#define pii pair<int, int>
const int N = 305;
const int inf = 300 * 300;
int n, m, k;
int a[N];
int b[N];
int f[N * N];
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m >> k;
int mn = 1e9;
int suma = 0;
int sumb = 0;
for (int i = 1; i <= n; i++) {
cin >> a[i];
suma += a[i];
mn = min(mn, a[i]);
}
for (int i = 1; i <= m; i++) {
cin >> b[i];
sumb += b[i];
}
if (mn < k) {
cout << "Impossible";
return 0;
}
for (int i = 1; i <= inf; i++) f[i] = -inf;
f[0] = 0;
for (int i = 1; i <= m; i++) {
for (int j = sumb; j >= b[i]; j--) {
f[j] = max(f[j], f[j - b[i]] + min(b[i], n));
}
}
for (int i = suma; i <= inf; i++) {
if (f[i] >= n * k) {
cout << i - suma;
return 0;
}
}
cout << "Impossible";
}
