#include <iostream>
#include <bitset>
#include <vector>
using namespace std;
typedef bitset<90000> bi;
int main() {
vector<int> v1;
vector<int> v2;
int sum = 0;
bool proper = true;
int N,M,K; cin>>N>>M>>K;
int sumK = N;
for (int i = 0; i < N; ++i) {
int a; cin>>a;
if(a<K)proper = false;
sum+=a;
}
for (int i = 0; i < M; ++i) {
int b; cin>>b;
if(b<=K) v1.push_back(b);
else v2.push_back(b);
}
if(!proper) {
cout<<"Impossible"<<endl;
exit(0);
}
bi init;
init[0]=true;
for (int b : v1) {
init = (init<<b)|init;
}
vector<bi> c(N);
for (int i = 0; i < 90000; ++i) {
if(init[i]) {
c[i/K][i]=true;
}
}
for(int b : v2) {
c[N-1]=c[N-1]|(c[N-1]<<b);
for (int i = N-2; i >-1; --i) {
c[i+1]=c[i+1]|(c[i]<<b);
}
}
for (int i = sum; i < 90000; ++i) {
if(c[N-1][i]) {
cout<<i-sum<<endl;
exit(0);
}
}
cout<<"Impossible"<<endl;
exit(0);
}
