#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ALL(x) x.begin(),x.end()
#define REV(x) x.rbegin(),x.rend()
typedef long long ll;
typedef tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update> intset;
int n,k,m,sum,res=1e9;
bool dp[90001],xd;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin >> n >> m >> k;
if(k>m){
cout << "Impossible";
return 0;
}
vector<int> food(n);
for(int i=0;i<n;i++){
cin >> food[i];
if(food[i]<k){
cout << "Impossible";
return 0;
}
sum+=food[i];
}
vector<int> chef(m);
for(int i=0;i<m;i++){
cin >> chef[i];
}
if(m<=15){
sort(REV(food));
for(int i=1;i<(1<<m);i++){
xd=true;
if(__builtin_popcount(i)<k){
continue;
}
intset temp;
for(int j=14;j>=0;j--){
if(i&(1<<j)){
temp.insert(chef[j]);
}
}
for(int j=0;j<n;j++){
if(temp.size()-k<0){
xd=false;
break;
}
for(int l=temp.size()-k;l<temp.size();l++){
auto p=temp.find_by_order(l);
int xx=*p-1;
temp.erase(p);
if(xx>0){
temp.insert(xx);
}
}
}
if(xd){
int nuesum=0;
for(auto u:temp){
nuesum+=u;
}
if(nuesum+n/k>=sum){
res=min(res,nuesum);
}
}
}
if(res==1e9){
cout << "Impossible";
}else{
cout << res;
}
}else{
dp[0]=true;
for(int i=0;i<m;i++){
for(int j=90000;j>=0;j--){
if(j-chef[i]>=0){
dp[j]|=dp[j-chef[i]];
}
}
}
for(int i=sum;i<=90000;i++){
if(dp[i]){
cout << i-sum;
return 0;
}
}
cout << "Impossible";
}
}
