//Proud of You//
#include <bits/stdc++.h>
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
using namespace std;
const int N = 3e2 + 17;
int n, m, k, a[N], b[N], f[7][N * N], sum;
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m >> k;
for (int i = 1; i <= n; ++i)
{
cin >> a[i];
sum += a[i];
}
for (int i = 1; i <= m; ++i)
{
cin >> b[i];
}
for (int i = 1; i <= m; ++i)
{
int t = i & 1;
for (int j = b[i]; j < N * N; ++j)
{
f[t][j] = max (f[t][j], f[t ^ 1][j - b[i]]) + min (n, b[i]);
}
}
for (int i = sum; i < N * N; ++i)
{
if (f[m & 1][i] >= n * k)
{
cout << i - sum;
return 0;
}
}
cout << "Impossible";
}
