#include <iostream>
using namespace std;
int cost[310];
int chefs[310];
int memo[310][91000];
int main()
{
int n, m, k, sum = 0, sum_of_chefs = 0;
cin >> n >> m >> k;
for(int i = 0; i < n; i++){
cin >> cost[i];
sum += cost[i];
}
for(int i = 0; i < m; i++){
cin >> chefs[i];
sum_of_chefs += chefs[i];
}
if(sum_of_chefs < sum){
cout << "Impossible" << endl;
return 0;
}
for(int i = 0; i < n; i++){
if(cost[i] < k){
cout << "Impossible" << endl;
return 0;
}
}
for(int i = 0; i < 310; i++)
for(int j = 0; j < 91000; j++)
memo[i][j] = -1;
for(int i = 0; i < 310; i++)
memo[i][0] = 0;
int najbolje = 99999997;
for(int i = 1; i <= m; i++){
for(int j = chefs[i - 1]; j <= sum_of_chefs; j++){
if(memo[i - 1][j] != -1)
memo[i][j] = memo[i - 1][j];
if(memo[i - 1][j - chefs[i - 1]] != -1)
memo[i][j] = max(memo[i][j], memo[i - 1][j - chefs[i - 1]] + min(chefs[i - 1], n));
if(j >= sum && memo[i][j] >= k*n){
najbolje = min(najbolje, j - sum);
}
}
}
if(najbolje != 99999997)
cout << najbolje << endl;
else
cout << "Impossible" << endl;
return 0;
}
