#include <bits/stdc++.h>
using namespace std;
const int maxn = 305, inf = 1e9 + 9;
int n, m, k, ans = inf, sum;
int a[maxn], b[maxn], dp[maxn][100005];
bool check = false;
void read_input() {
cin >> n >> m >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
sum += a[i];
check |= (a[i] < k);
}
for (int i = 1; i <= m; i++)
cin >> b[i];
}
void solve() {
memset(dp, -63, sizeof(dp));
dp[0][0] = 0;
for (int i = 1; i <= m; i++)
for (int j = 0; j < 100005; j++) {
dp[i][j] = dp[i - 1][j];
if (j - b[i] >= 0)
dp[i][j] = max(dp[i][j], dp[i - 1][j - b[i]] + min(n, b[i]));
if (j >= sum && dp[i][j] >= n * k)
ans = min(ans, j - sum);
}
if (check || ans >= inf)
cout << "Impossible";
else
cout << ans;
}
int32_t main() {
ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
read_input(), solve();
return 0;
}
