#include<bits/stdc++.h>
#include<unordered_map>
#define rep(i,a,b) for(int i=int(a);i<int(b);i++)
#define rrep(i,a,b) for(int i=int(a);i>int(b);i--)
#define trav(a,v) for(auto& a: v)
#define sz(v) v.size()
#define all(v) v.begin(),v.end()
#define vi vector<int>
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const long long inf = 1e15;
using namespace std;
int main() {
cin.sync_with_stdio(false);
ll n, m, k;
cin >> n >> m >> k;
vector<ll> v(n);
vector<ll> v2(m);
rep(i, 0, n) {
cin >> v[i];
if (v[i] < k) {
cout << "Impossible" << endl;
return 0;
}
}
rep(i, 0, m)cin >> v2[i];
ll sum = 0;
rep(i, 0, n)sum += v[i];
sort(all(v2), greater<>());
vector <ll>dp0(1e5,-inf);
dp0[0]= 0;;
ll ans = inf;
ll sumv2 = 0;
ll sumk = 0;
rep(i, 0, m) {
rrep(j, sumv2,-1) {
dp0[j + v2[i]] = max(dp0[j + v2[i]], dp0[j] + min(n, v2[i]));
}
sumv2 += v2[i];
sumk++;
}
rep(i, sum, sumv2+1) {
if (dp0[i] >= n * k) {
ans = i;
break;
}
}
if (ans == inf)cout << "Impossible" << endl;
else cout << ans - sum << endl;
return 0;
}
