#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;
sort(b.begin(), b.end());
int j = 0;
while (j < m && b[j] < n) j++;
const int A = 300 * m;
vector<bool> sm(A + 1); sm[0] = 1;
for (int i = 0; i < j; i++){
for (int t = A; t >= 0; t--){
if (sm[t]){
sm[t + b[i]] = 1;
}
}
}
vector<int> all;
for (int i = 0; i <= A; i++){
if (sm[i]) all.pb(i);
}
int M = m - j;
vector<vector<bool>> can(M + 1, vector<bool>(A + 1)); can[0][0] = 1;
for (int i = j; i < m; i++){
for (int t = M; t >= 0; t--){
for (int x = A; x >= 0; x--){
if (can[t][x]){
can[t + 1][x + b[i]] = 1;
}
}
}
}
int out = 1e9;
for (int cc = 0; cc <= M; cc++){
vector<int> low(A + 1, -1); low[A] = (can[cc][A]) ? A : -1;
for (int i = A - 1; i >= 0; i--){
if (!can[cc][i]){
low[i] = low[i + 1];
}
else {
low[i] = i;
}
}
for (int sl: all){
if (sl >= (S2 - n * cc)){
int x = low[max(0, S1 - sl)];
if (x != -1){
out = min(out, sl + x);
}
}
}
}
if (out == 1e9){
cout<<"Impossible"<<"\n";
}
else {
cout<<out - S1<<"\n";
}
}
