#include <bits/stdc++.h>
using namespace std;
int n, m, k, a[301], b[301];
int dp[301][90001];
void bad () {
cout << "Impossible\n";
exit(0);
}
int main () {
cin >> n >> m >> k;
for (int i = 0; i < n; i++) cin >> a[i];
for (int j = 0; j < m; j++) cin >> b[j];
int pp = *min_element(a, a + n);
if (pp < k || m < k) bad();
for (int i = 1; i <= 90000; i++) dp[0][i] = -1e9;
for (int i = 1; i <= m; i++) {
for (int j = 0; j <= 90000; j++) {
if (j < b[i - 1]) {
dp[i][j] = dp[i - 1][j]; continue;
}
dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - b[i - 1]] + min(b[i - 1], n));
}
}
int mn = 1e9; int sum = 0; for (int i = 0; i < n; i++) sum += a[i];
for (int i = sum; i <= 90000; i++) {
if (dp[m][i] >= n * k) {
mn = i; break;
}
}
mn -= sum;
if (mn >= 1e8) bad();
cout << mn << '\n';
}
