#include <iostream>
#include <algorithm>
#include <cmath>
#include <map>
#include <climits>
#include <vector>
#include <queue>
#include <utility>
#include <iomanip>
#include <cstring>
#include <fstream>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> ii;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
ll n, m, k;
cin >> n >> m >> k;
ll a[n], b[m];
ll sum = 0;
for (ll i = 0; i < n; i++){
cin >> a[i];
sum += a[i];
if (a[i] < k){
cout << "Impossible";
return 0;
}
}
for (ll i = 0; i < m; i++)
cin >> b[i];
if (k > m){
cout << "Impossible";
return 0;
}
vector<ll> dp(90001, (ll)-1e6);
dp[0] = 0;
for (ll i = 0; i < m; i++){
for (ll j = 90000 - b[i]; j >= 0 ; j--){
dp[j + b[i]] = max(dp[j + b[i]], dp[j] + min(n, b[i]));
}
}
for (ll i = sum; i < 90001; i++){
if (dp[i] >= n*k){
cout << i - sum << endl;
return 0;
}
}
cout << "Impossible";
return 0;
}
