#include <bits/stdc++.h>
using namespace std;
/*
#pragma GCC optimize("O3")
#include <bitset>
#pragma GCC target("avx2")*/
#define fi first
#define se second
#define int long long
typedef long long ll;
typedef long double ld;
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
int inf = 1e15;
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, m, k;
cin >> n >> m >> k;
vector<int> a(n);
vector<int> b(m);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
for (int i = 0; i < m; i++) {
cin >> b[i];
}
int sum = 0;
bool ok = 1;
for (int i = 0; i < n; i++) {
sum += a[i];
if (a[i] < k)
ok = 0;
}
vector<int> s;
for (int i = 0; i < m; i++) {
s.push_back(b[i]);
}
if (!ok) {
cout << "Impossible" << '\n';
return 0;
}
vector<int> dp(300 * 300 + 100, -1);
dp[0] = 0;
int mini = inf;
for (int i = 0; i < s.size(); i++) {
int val = s[i];
for (int j = dp.size() - 1; j >= val; j--) {
if (dp[j - val] != -1)
dp[j] = max(dp[j], dp[j - val] + min(n, val));
}
}
for (int j = sum; j < dp.size(); j++) {
if (dp[j] >= n * k) {
mini = j;
break;
}
}
if (mini == inf) {
cout << "Impossible" << '\n';
} else {
cout << mini - sum << '\n';
}
}
