#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ordered_set <int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define ordered_multiset <int, null_type, less_equal <int>, rb_tree_tag, tree_order_statistics_node_update>
#define int long long
#define double long double
#define pii pair <int, int>
#define tiii tuple <int, int, int>
#define tiiii tuple <int, int, int, int>
#define emb emplace_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define iShowSpeed cin.tie(NULL)->sync_with_stdio(false)
#define matrix vector <vector <int>>
#define mat(n, m) vector <vector <int>> (n, vector <int> (m));
const int mod = 1e9 + 7;
const int inf = 1e18;
const matrix II = {{1, 0}, {0, 1}};
const int N = 2e5 + 5;
void solve(){
int n, m, k; cin >> n >> m >> k;
vector <int> a(n + 1), b(m + 1);
for (int i = 1; i <= n; i++) {
cin >> a[i];
if (a[i] < k) return cout << "Impossible\n", void();
}
for (int i = 1; i <= m; i++) cin >> b[i];
int sz = 4 * accumulate(all(a), 0ll);
int dp[sz + 1]; memset(dp, 0, sizeof dp);
for (int i = 1; i <= m; i++) {
for (int j = sz; j >= b[i]; j--) {
dp[j] = max(dp[j], dp[j - b[i]] + min(b[i], n));
}
}
int ans = inf;
for (int i = sz/4; i <= sz; i++) {
if (dp[i] >= k * n) {
ans = i - sz/4;
break;
}
}
if (ans == inf) cout << "Impossible\n";
else cout << ans << "\n";
}
int32_t main(){
iShowSpeed;
// int q; cin >> q; while (q--)
solve();
}
