#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define ull unsigned long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define fi first
#define se second
const int N = 3e2 + 5;
int a[N], b[N], dp[N * N];
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
int n, m, k, sum1 = 0, sum2 = 0;
cin >> n >> m >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
if (a[i] < k) {
cout << "Impossible\n";
return 0;
}
sum1 += a[i];
}
for (int i = 1; i <= m; i++) {
cin >> b[i];
sum2 += b[i];
}
for (int i = 1; i <= sum2; i++) dp[i] = -1e9;
for (int i = 1; i <= m; i++) {
for (int j = sum2; j >= b[i]; j--) dp[j] = max(dp[j], dp[j - b[i]] + min(b[i], n));
}
for (int i = sum1; i <= sum2; i++) {
if (dp[i] >= n * k) {
cout << i - sum1 << "\n";
return 0;
}
}
cout << "Impossible\n";
}
