#include <bits/stdc++.h>
#define fr(i, a, b) for (int i = (a); i <= (b); ++i)
#define rf(i, a, b) for (int i = (a); i >= (b); --i)
#define fe(x, y) for (auto& x : y)
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(), (x).end()
#define pw(x) (1LL << (x))
#define sz(x) (int)(x).size()
using namespace std;
mt19937_64 rng(228);
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template <typename T>
using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define fbo find_by_order
#define ook order_of_key
template <typename T>
bool umn(T& a, T b) {
return a > b ? a = b, 1 : 0;
}
template <typename T>
bool umx(T& a, T b) {
return a < b ? a = b, 1 : 0;
}
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template <typename T>
using ve = vector<T>;
const int N = 305;
const int M = 305 * 305;
int n, m, k, sumA;
int a[N], b[N];
int dp[M];
//int ndp[M];
int main() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#else
ios::sync_with_stdio(0);
cin.tie(0);
#endif
cin >> n >> m >> k;
fr (i, 1, n) {
cin >> a[i];
if (a[i] < k) {
cout << "Impossible\n";
return 0;
}
sumA += a[i];
}
fr (i, 1, m) {
cin >> b[i];
}
{
fr (i, 0, M - 1) {
dp[i] = -1e9;
}
dp[0] = 0;
fr (i, 1, m) {
rf (sum, M - 1, b[i]) {
umx(dp[sum], dp[sum - b[i]] + min(b[i], n));
}
}
fr (i, sumA, M - 1) {
if (dp[i] >= n * k) {
cout << i - sumA << "\n";
return 0;
}
}
cout << "Impossible\n";
}
// int best = 2e9;
// fr (mask, 0, pw(m) - 1) {
// int sum = 0;
// int sum2 = 0;
// fr (i, 1, m) {
// if (mask & pw(i - 1)) {
// sum += b[i];
// sum2 += min(n, b[i]);
// }
// }
//
// if (sum >= sumA && sum2 >= n * k) {
// umn(best, sum - sumA);
// }
// }
//
// if (best == 2e9) {
// cout << "Impossible\n";
// } else {
// cout << best << "\n";
// }
return 0;
}
