#include <bits/stdc++.h>
using namespace std;
#define MAXN 305
#define int long long
int n,m,k;
int a[MAXN],b[MAXN];
int number[MAXN];
queue<int> q;
int32_t main()
{
cin>>n>>m>>k;
for (int i=1;i<=n;i++) cin>>a[i];
for (int i=1;i<=m;i++) cin>>b[i];
int suma=0;for (int i=1;i<=n;i++) suma+=a[i];
if (m<=15)
{
int answer=INT_MAX;
for (int maska=0;maska<(1<<m);maska++)
{
int sumb=0;for (int i=1;i<=n;i++) {number[i]=0;q.push(i);}
for (int bit=0;bit<m;bit++)
{
if (!(maska&(1<<bit))) continue;
sumb+=b[bit+1];
for (int num=1;num<=min(n,b[bit+1]);num++)
{
if (q.empty()) break;
int node=q.front();q.pop();
number[node]++;
if (number[node]<a[node]) q.push(node);
}
}
while (!q.empty()) q.pop();
bool valid=true;
for (int node=1;node<=n;node++)
{
if (number[node]<k) {valid=false;break;}
}
if (valid==true and sumb>=suma) answer=min(answer,sumb-suma);
}
if (answer==INT_MAX) {cout<<"Impossible"<<endl;return 0;}
else {cout<<answer<<endl;return 0;}
}
}
