#include <iostream>
#include <vector>
using namespace std;
int main(){
int n, m ,k;
cin >> n >> m >> k;
int suma = 0;
int mini = 1<<29;
vector <int> a(n);
for (int i = 0; i < n; i++){
cin >> a[i];
mini = min(mini,a[i]);
suma += a[i];
}
int sumb = 0;
vector <int> b(m);
for (int i = 0; i < m; i++){
cin >> b[i];
}
if (mini < k){
cout << "Impossible";
return 0;
}
if (k > m){
cout << "Impossible";
return 0;
}
vector <int> dp(90001,-1*(1<<29));
dp[0] = 0;
for (int i = 0; i < m; i++){
int dod = b[i];
sumb += dod;
for (int j = sumb; j >= 0; j--){
dp[j+dod] = max(dp[j+dod], dp[j] + min(dod,n));
}
}
for (int i = suma; i <= sumb; i++){
//cout << dp[i] << endl;
if (dp[i] >= n*k){
cout << i - suma;
return 0;
}
}
cout << "Impossible";
}
