#ifndef local
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("O3")
#endif
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
using ll = long long;
#define int ll
using pii = pair<int, int>;
using pll = pair<ll,ll>;
using str = string;
using ld = long double;
using hash_map =gp_hash_table<int, int>;
using hash_set= gp_hash_table <int, null_type>;
auto sd = std::chrono::high_resolution_clock::now().time_since_epoch().count();
mt19937 rnd(sd);
typedef tree<ll, null_type, less<>, rb_tree_tag,
tree_order_statistics_node_update> ord_set;
const ll maxn = 3e5+8;
const ll inf = 1e18;
void solve1() {
ll n;
cin >> n; ll m, k;cin>>m>>k;
vector<ll> a(n);
ll sum_ai = 0;
bool impossible = false;
for (int i =0; i<n ;i++){
cin>>a[i];
if (a[i]<k) impossible = true;
sum_ai += a[i];
}
vector<ll>b(m);
ll sum=0;
for (int i =0; i < m; i++){
cin>>b[i];
sum += b[i];
}
if (impossible){
cout<<"Impossible\n";
return;
}
vector<vector<ll>> dp(m+1, vector<ll>(sum+1, -1));
dp[0][0] = 0;
for (int i = 1; i <= m; i++){
for (int j = 0; j <= sum; j++){
if (dp[i-1][j]==-1){
continue;
}
dp[i][j] = max(dp[i-1][j], dp[i][j]);
if (j+b[i-1]<=sum) dp[i][j+b[i-1]] = max(dp[i][j+b[i-1]], dp[i-1][j]+min(b[i-1], n));
}
}
for (int j = sum_ai; j <= sum; j++){
if (dp[m][j]>=n*k){
cout<< j-sum_ai<<endl;
return;
}
}
cout<<"Impossible\n";
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
#ifdef local
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
int t1 = 1;
while (t1) solve1(), t1--;
#ifdef local
printf_s("\n%.5f s", (double) clock() / CLOCKS_PER_SEC);
#endif
}
