#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <fstream>
#include <algorithm>
#include <string>
using namespace std;
int n, m, k, sum = 0, last[90001], dp[90001] = {};
int main() {
ios_base::sync_with_stdio(false);
cin >> n >> m >> k;
for (int i = 0; i < n; i++){
int a; cin >> a;
if (a < k){
cout << "Impossible" << endl; return 0;
}
sum += a;
}
last[0] = 0;
for (int i = 1; i <= 90000; i++){
last[i] = -1; dp[i] = -1;
}
for (int i = 0; i < m; i++){
int c; cin >> c;
for (int j = 0; j <= 90000-c; j++){
if (last[j] >= 0){
dp[j] = max(dp[j], last[j]);
dp[j+c] = max(dp[j+c], last[j]+min(n, c));
}
}
swap(dp, last);
for (int j = 0; j <= 90000; j++){
dp[j] = -1;
}
}
for (int i = sum; i <= 90000; i++){
if (last[i] >= n*k){
cout << i-sum; return 0;
}
}
cout << "Impossible" << endl;
}
