#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
const int maxn5 = 7e3 + 10;
const ll inf = 1e18;
const int masum = 1e5 + 10;
ll a[maxn5], b[maxn5];
ll n, m, k;
ll dp[masum];
inline void solve(){
fill(dp, dp + masum, -inf);
dp[0] = 0;
for(int i = 0; i < m; i++){
for(int j = masum - 1; j >= b[i]; j--){
dp[j] = max(dp[j], dp[j - b[i]] + min(n, b[i]));
}
}
ll sum = 0;
for(int i = 0; i < n; i++)
sum += a[i];
for(int i = sum; i < masum; i++) if(dp[i] >= n * k){
cout << i - sum << '\n';
exit(0);
}
cout << "Impossible" << endl;
exit(0);
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n >> m >> k;
ll sum = 0;
for(int i = 0; i < n; i++){
cin >> a[i];
if(a[i] < k)
return cout << "Impossible" << endl, 0;
sum += a[i];
}
for(int i = 0; i < m; i++)
cin >> b[i];
if(true)
solve();
ll ans = inf;
for(int mask = 0; mask < (1 << m); mask++) if(__builtin_popcount(mask) >= k){
ll sum1 = 0, sum2 = 0;
for(int i = 0; i < m; i++) if((mask >> i)&1){
sum1 += min(n, b[i]);
sum2 += b[i];
}
if(sum1 >= n * k && sum2 >= sum && ans >= sum2){
ans = sum2;
//cout << mask << ' ' << sum1 << ' ' << sum2 << endl;
}
}
if(ans == inf)
cout << "Impossible" << endl;
else
cout << ans - sum << endl;
}
