#include <bits/stdc++.h>
using namespace std;
#define int long long
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
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];
}
for(int i = 1; i <= m; i++) {
cin >> b[i];
}
for(int i = 1; i <= n; i++) {
if(a[i] < k) {
cout << "Impossible\n";
return;
}
}
int sum = 0;
for(int i = 1; i <= m; i++) {
sum += b[i];
}
vector<int> dp(sum + 1, INT_MIN);
dp[0] = 0;
for(int i = 1; i <= m; i++) {
for(int j = sum - b[i]; j >= 0; j--) {
dp[j + b[i]] = max(dp[j + b[i]], dp[j] + min(n, b[i]));
}
}
int min_req = 0;
for(int i = 1; i <= n; i++) {
min_req += a[i];
}
/*for(int i = 0; i <= sum; i++) {
cout << dp[i] << " ";
}
cout << "\n";*/
for(int i = min_req; i <= sum; i++) {
if(dp[i] >= n * k) {
cout << i - min_req << "\n";
return;
}
}
cout << "Impossible\n";
}
int32_t main() {
ios::sync_with_stdio(0);
cin.tie(0);
Solve();
return 0;
}
