#include <bits/stdc++.h>
using namespace std;
const int MXN = 301;
const int INF = 1e9;
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, m, k;
cin >> n >> m >> k;
vector<int> a(n), b(m);
for(int i = 0; i < n; i++)
cin >> a[i];
for(int i = 0; i < m; i++)
cin >> b[i];
if(*min_element(a.begin(), a.end()) < k){
cout << "Impossible\n";
return 0;
}
vector<int> dp(MXN*MXN, -INF);
dp[0] = 0;
for(int i = 0; i < m; i++){
for(int W = MXN*MXN - 1; W >= b[i]; --W)
dp[W] = max(dp[W], dp[W-b[i]] + min(b[i], n));
}
int sum = accumulate(a.begin(), a.end(), 0);
int ans = INF;
for(int W = sum; W < MXN*MXN; W++)
if(dp[W] >= n*k)
ans = min(ans, W - sum);
cout << (ans != INF ? to_string(ans) : "Impossible") << '\n';
return 0;
}
