#include <bits/stdc++.h>
/// author: LilPluton auuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
#define OPT ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define intt long long
#define ll long long
#define pb push_back
#define arr array
#define vll vector<int>
#define fi first
#define se second
#define rep(i,j,k) for(int i = j; i <= k; ++i)
#define all(a) a.begin(),a.end()
#define pii pair<int,int>
#define endll '\n'
using namespace std;
const ll INF = 1e18;
const int N = 305 * 305;
ll n, m, k, sum, chefsum;
ll a[N], chef[N];
ll dp[N];
signed main()
{
cin >> n >> m >> k;
for(ll i = 1; i <= n; ++i)
cin >> a[i], sum += a[i];
sort(a + 1, a + n + 1);
for(ll i = 1; i <= m; ++i)
cin >> chef[i];
sort(chef + 1, chef + 1 + m);
if(m < k || a[1] < k)
{
cout << "Impossible" << endll;
return 0;
}
for (ll i = 1; i <= m; ++i) {
for (int j = N; j >= chef[i]; --j) {
if (j == chef[i] || dp[j - chef[i]]) {
dp[j] = max(dp[j], dp[j - chef[i]] + min(chef[i], n));
}
}
}
for(ll i = sum; i <= N; ++i)
{
if(dp[i] >= n * k)
{
cout << i - sum << endll;
return 0;
}
}
cout << "Impossible" << endll;
}
