#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 5;
const int maxN = 305;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, m, k;
cin >> n >> m >> k;
vector<int> a(n), b(m);
for(int& i : a) {
cin >> i;
}
for(int& i : b) {
cin >> i;
}
int ans = INF;
for(int i : a) {
if (i < k) {
cout << "Impossible\n";
exit(0);
}
}
int time = accumulate(a.begin(), a.end(), 0);
vector<int> last(maxN*maxN, -INF);
last[0] = 0;
vector<int> curr(maxN*maxN, -INF);
for(int i = 1; i <= m; i++) {
for(int j = 0; j < maxN*maxN; j++) {
curr[j] = last[j];
if (j-b[i-1] < 0) continue;
curr[j] = max(curr[j], last[j-b[i-1]] + min(n, b[i-1]));
if (curr[j] >= k*n && j >= time && j-time < ans) {
ans = j-time;
}
}
last = curr;
}
if (ans == INF) {
cout << "Impossible\n";
} else {
cout << ans << "\n";
}
return 0;
}
