#include <iostream>
#include <vector>
#include <algorithm>
#include <cassert>
#pragma GCC optimize("O3","unroll-loops")
#pragma GCC target("avx2")
using ll = long long;
#define debug(x) #x << " = " << x << '\n'
const int MAX = 300;
const int INF = 1e9;
int dp[MAX * MAX + 1];
int main() {
int n, m, k;
std::cin >> n >> m >> k;
int sumA = 0;
for (int i = 0; i < n; i++) {
int x;
std::cin >> x;
if (x < k) {
std::cout << "Impossible";
return 0;
}
sumA += x;
}
dp[0] = 0;
for (int s = 1; s <= MAX * MAX; s++) {
dp[s] = -INF;
}
int sum = 0;
for (int i = 0; i < m; i++) {
int x;
std::cin >> x;
sum += x;
int me = std::min(n, x);
for (int s = sum; s >= x; s--) {
dp[s] = std::max(dp[s], dp[s - x] + me);
}
}
for (int s = sumA; s <= sum; s++) {
if (dp[s] >= n * k) {
std::cout << s - sumA;
return 0;
}
}
std::cout << "Impossible";
return 0;
}
