#include<bits/stdc++.h>
using namespace std;
#define int long long
void fun () {
int n, k, m;
cin >> n >> m >> k;
vector<int> a(n + 1), b(m + 1);
int s = 0, s1 = 0;
for (int i = 1; i <= n; i++) cin >> a[i], s += a[i];
for (int i = 1; i <= m; i++) cin >> b[i], s1 += b[i];
for (int i = 1; i <= n; i++) {
if (a[i] < k) {
cout << "Impossible\n";
return;
}
}
if (k > m) {
cout << "Impossible\n";
return;
}
vector<vector<int>> dp(m + 1, vector<int>(s1 + 1));
for (int i = 1; i <= m; i++) {
for (int j = 0; j <= s1; j++) {
if (j - b[i] >= 0) {
dp[i][j] = dp[i - 1][j - b[i]] + min(b[i], n);
}
dp[i][j] = max(dp[i][j], dp[i - 1][j]);
}
}
for (int i = s; i <= s1; i++) {
if (dp[m][i] >= n * k) {
cout << i - s << endl;
return;
}
}
cout << "Impossible";
}
signed main () {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int tt = 1;
//cin >> tt;
while (tt--) fun();
return 0;
}
