#include <bits/stdc++.h>
#include <fstream>
#define endl '\n'
#define mod 1668223877717
#define INF -100000000000000000
//#define ll long long
//#define cin fin
//#define cout fout
using namespace std;
//ofstream fout("convention.out");
//ifstream fin("convention.in");
const int M = 9e4 + 5;
int n, m, k;
pair<bool,long long> dp[M] = {};
void add(int x)
{
for(int i = M-1; i >= x; i--)
{
if(dp[i-x].first == 1)
{
dp[i].first = 1;
dp[i].second = max(dp[i].second,dp[i-x].second+min(n,x));
}
}
}
int main()
{
ios_base::sync_with_stdio(0);cout.tie(0);cin.tie(0);
cin >> n >> m >> k;
int meal[n], chef[m];
long long sum = 0;
bool ok = true;
dp[0].first = 1;
for(int i = 0; i < n; i++)
{
cin >> meal[i];
if(meal[i] < k)
ok = false;
sum += meal[i];
}
for(int i = 0; i < m; i++)
{
cin >> chef[i];
add(chef[i]);
}
if(ok == false)
{
cout << "Impossible";
return 0;
}
for(int i = sum; i < M; i++)
{
if(dp[i].second >= n*k)
{
cout << i-sum;
return 0;
}
}
cout << "Impossible";
return 0;
}
