#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define forn(i,n) for(int i=0;i<n;++i)
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define f first
#define s second
#define pi pair<int,int>
#define vii(a,n) vector<int>a(n);forn(i,n)cin>>a[i];
const int inf = 1e9;
void solve() {
int n,m,k; cin>>n>>m>>k;
vii(a,n);
vii(b,m);
if (k==1) {
vector<int> dp(1e5,0);
dp[0]=1;
int s=0; forn(i,n) s+=a[i];
for(auto&x:b) {
for (int i=9e4; i>=0; --i) {
dp[i+x]|=dp[i];
}
}
for (int i=s; i<1e5; ++i) {
if (dp[i]) {
cout<<i-s;
return;
}
}
cout<<"Impossible";
return;
}
if (m>15) exit(0);
if (k>m) {
cout<<"Impossible";
return;
}
forn(i,n) if (a[i]<k) {
cout<<"Impossible";
return;
}
int s=0;
for(auto&x:a) s+=x;
for(auto&x:b) s-=x;
if (s>0) {
cout<<"Impossible";
return;
}
int z=0;
for(auto&x:a) z+=x;
int ans=inf;
for (int mask=0; mask<(1<<m); ++mask) {
if (__builtin_popcount(mask) < k) continue;
vector<int> f;
forn(i,m) if ((mask>>i)&1) f.pb(b[i]);
int sum=0;
for(auto&x:f) sum+=x;
if (sum<z) continue;
sort(rall(f));
forn(i,n) {
forn(j,k) f[j]--;
sort(rall(f));
}
if (f.back()<0) continue;
ans=min(ans,sum-z);
}
if (ans==inf) cout<<"Impossible";
else cout<<ans;
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
solve();
}
