#include <bits/stdc++.h>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
//#define int long long
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;
int32_t main() {
int n, m, k;
cin >> n >> m >> k;
vector<int> A(n+1), B(m+1);
for(int i=1; i<=n; i++) cin >> A[i];
for(int i=1; i<=m; i++) cin >> B[i];
sort(A.begin() + 1, A.end());
sort(B.begin() + 1, B.end());
if(A[1] < k || m < k) {
cout << "impossible\n";
return 0;
}
if(k == 1) {
//check possible sums, get first possible >= sum(A)
ll sum = 0;
for(int i=1; i<=n; i++) sum += A[i];
bitset<100005> bs;
bs[0] = 1;
for(int i=1; i<=m; i++) bs |= (bs << B[i]);
for(int i=sum; i<=300*300; i++) {
if(bs[i]) {
cout << i - sum << '\n';
return 0;
}
}
cout << "impossible\n";
return 0;
}
return 0;
}
