#pragma GCC optimize("O3", "unroll-loops") // "Ofast"
#pragma GCC target("avx2", "bmi", "bmi2", "lzcnt", "popcnt")
#include <bits/stdc++.h>
#define int long long
#define vt vector
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define f first
#define s second
#define dbg(x) cerr << #x << " = " << x << '\n'
#define bit(x, i) ((x) >> (i) & 1)
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
const int N = 1e6 + 5, mod = 1e9 + 7;
const ll inf = 1e18 + 7;
const ld eps = 1e-6;
ll add (ll a, ll b) {
a += b;
if (a < 0) a += mod;
if (a >= mod) a -= mod;
return a;
}
ll mul (ll a, ll b) {
a *= b;
if (a >= mod) a %= mod;
return a;
}
int n, m, k, a[N], b[N], dp[N];
void solve () {
cin >> n >> m >> k;
int suma = 0, sumb = 0;
for (int i = 1; i <= n; i++) {
cin >> a[i];
if (a[i] < k) cout << "Impossible\n", exit(0);
suma += a[i];
}
for (int i = 1; i <= m; i++) cin >> b[i], sumb += b[i];
fill(dp, dp + N, -inf);
dp[0] = 0;
for (int i = 1; i <= m; i++) {
for (int w = sumb; w >= b[i]; w--) dp[w] = max(dp[w], dp[w - b[i]] + min(b[i], n));
}
for (int w = suma; w <= sumb; w++) {
if (dp[w] >= n * k) {
cout << w - suma << '\n';
return;
}
}
cout << "Impossible\n";
cout << '\n';
}
bool testcases = 0;
signed main() {
#ifdef AMIR
freopen(".in", "r", stdin);
freopen(".out", "w", stdout);
#endif
cin.tie(0) -> sync_with_stdio(0);
int test = 1;
if (testcases) cin >> test;
for (int cs = 1; cs <= test; cs++) {
solve();
}
}
