// ¯\_(ツ)_/¯
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
#define all(x) (x).begin(),(x).end()
#define X first
#define Y second
#define sep ' '
#define endl '\n'
#define debug(x) cerr << #x << ": " << x << endl;
const ll MAXN = 300 + 3;
const ll INF = 1e9;
const ll MOD = 1e9 + 7; // 998244353; // 1e9 + 9;
int dp[MAXN][MAXN * MAXN], n, m, k, B[MAXN], A[MAXN], s;
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n >> m >> k;
for (int i = 1; i <= n; i++) {
cin >> A[i];
if (A[i] < k) return cout << "Impossible" << endl, 0;
s += A[i];
}
for (int j = 1; j <= m; j++) cin >> B[j];
fill(dp[0], dp[0] + MAXN * MAXN, -INF);
dp[0][0] = 0;
for (int i = 1; i <= m; i++) {
for (int h = 0; h < MAXN * MAXN; h++) {
dp[i][h] = dp[i - 1][h];
int c = min(n, B[i]);
if (h >= B[i]) dp[i][h] = max(dp[i][h], dp[i - 1][h - B[i]] + c);
}
}
for (int i = s; i < MAXN * MAXN; i++)
if (dp[m][i] >= n * k)
return cout << i - s << endl, 0;
cout << "Impossible" << endl;
return 0;
}
