#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
#define long unsigned long
#define pb push_back
#define mp make_pair
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define lb lower_bound
#define ub upper_bound
#define sz(v) int((v).size())
#define do_not_disturb ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl '\n'
vector <bitset <100001>> dp(301);
void impossible() {
cout << "Impossible" << endl;
exit(0);
}
void solve() {
int n, m, k;
cin >> n >> m >> k;
vector <int> a(n), b(m+1);
for (auto &to : a) cin >> to;
for (int i = 1; i <= m; i++) {
cin >> b[i];
}
int dishes = 0, chefs = 0;
for (auto to : a) dishes += to;
if (*min_element(all(a)) < k) impossible();
vector <vector <int>> dp(m+1, vector <int> (90000 + 1, -2e9));
dp[0][0] = 0;
for (int i = 1; i <= m; i++) {
chefs += b[i];
for (int j = chefs; j >= 0; j--) {
if (j >= b[i])
dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - b[i]] + min(n, b[i]));
else dp[i][j] = dp[i - 1][j];
}
}
for (int j = dishes; j <= chefs; j++) {
if (dp[m][j] >= n * k) {
cout << j - dishes;
return;
}
}
impossible();
}
int main() {
do_not_disturb
int t = 1;
//~ cin >> t;
while (t--) {
solve();
}
return 0;
}
