#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define pb push_back
#define ff first
#define ss second
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, m, k; cin>>n>>m>>k;
vector<int> a(n + 1);
for (int i = 1; i <= n; i++){
cin>>a[i];
}
vector<int> b(m);
for (int i = 0; i < m; i++){
cin>>b[i];
}
int S1 = 0;
for (int i = 1; i <= n; i++){
if (a[i] < k){
cout<<"Impossible"<<"\n";
return 0;
}
S1 += a[i];
}
int S2 = k * n, out = 1e9;
for (int i = 1; i < (1 << m); i++){
int s1 = 0, s2 = 0;
for (int j = 0; j < m; j++){
if ((i >> j) & 1){
s1 += b[j];
s2 += min(n, b[j]);
}
}
if (s1 >= S1 && s2 >= S2){
out = min(out, s1);
}
}
if (out == 1e9){
cout<<"Impossible"<<"\n";
}
else {
cout<<out - S1<<"\n";
}
}
