#include <bits/stdc++.h>
#include <fstream>
#define endl '\n'
#define mod 32768
#define INF 100000000
//#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;
const int N = 300 + 5;
int n, m, k;
pair<bool,int> dp[M][N] = {};
void add(int x)
{
for(int i = M-1; i >= x; i--)
{
for(int j = 1; j < N; j++)
{
if(dp[i-x][j-1].first)
{
dp[i][j].first = 1;
if(x >= k)
dp[i][j].second += dp[i-x][j-1].second+1;
else
dp[i][j].second = dp[i-x][j-1].second;
}
}
}
}
int main()
{
cin >> n >> m >> k;
int meal[n], chef[m];
dp[0][0].first = 1;
long long sum = 0;
bool ok = true;
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(m < k || ok == false)
{
cout << "Impossible";
return 0;
}
for(int i = sum; i < M; i++)
{
for(int j = k; j < N; j++)
{
if(dp[i][j].first == 1 && dp[i][j].second >= k)
{
cout << i-sum;
return 0;
}
}
}
cout << "Impossible";
return 0;
}
