#include <bits/stdc++.h>
using namespace std;
const int MAXN = 310;
const int INF = 1e9 + 10;
int dp[MAXN][MAXN * MAXN];
int a[MAXN], b[MAXN];
int n, m, k;
void solve() {
cin >> n >> m >> k;
int sum_a = 0, sum_b = 0;
for (int i = 1; i <= n; i++) {
cin >> a[i];
sum_a += a[i];
if (a[i] < k) {
cout << "Impossible\n";
return;
}
}
for (int i = 1; i <= m; i++) {
cin >> b[i];
sum_b += b[i];
}
for (int i = 0; i <= m; i++) {
for (int j = 0; j <= sum_b; j++) {
dp[i][j] = -INF;
}
}
dp[0][0] = 0;
for (int i = 1; i <= m; i++) {
for (int j = 0; j <= sum_b; j++) {
dp[i][j] = dp[i - 1][j];
if (j >= b[i]) {
dp[i][j] = max(dp[i][j], dp[i - 1][j - b[i]] + min(b[i], n));
}
}
}
for (int r = sum_a; r <= sum_b; r++) {
for (int i = 1; i <= m; i++) {
if (dp[i][r] >= k * n) {
cout << r - sum_a << "\n";
return;
}
}
}
cout << "Impossible\n";
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
solve();
return 0;
}
