#include <bits/stdc++.h>
using namespace std;
#define debug(x) {cout << #x << ": "; for (auto it : x) cout << it << " ";cout << enl;}
#define fast ios::sync_with_stdio(0);cin.tie(0);
typedef long long ll;
#define f first
#define s second
#define MOD 998244353
#define LOGN 20
#define MAXN 305
int dp[MAXN][90005];
vector<int> meal, chef;
int main() {
fast
int N, M, K;
cin >> N >> M >> K;
meal = vector<int>(N+1);
chef = vector<int>(M+1);
int sum = 0;
for (int i = 1; i <= N; i++) {
cin >> meal[i];
sum += meal[i];
}
for (int i = 1; i <= M; i++)
cin >> chef[i];
for (int i = 0; i <= M; i++) {
for (int total = 0; total <= 90000; total++)
dp[i][total] = -1e8;
}
dp[0][0] = 0;
for (int i = 1; i <= M; i++) {
for (int total = 0; total <= 90000; total++) {
dp[i][total] = dp[i-1][total];
if (total - chef[i] >= 0)
dp[i][total] = max(dp[i][total], dp[i-1][total - chef[i]] + min(chef[i], N));
}
}
int ans = INT_MAX;
for (int total = sum; total <= 90000; total++) {
if (dp[M][total] >= N * K)
ans = min(ans, total - sum);
}
if (ans == INT_MAX)
cout << "Impossible\n";
else
cout << ans << "\n";
}
