#include <bits/stdc++.h>
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define int long long
using namespace std;
const int MAXB=305;
signed main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int n,m,K; cin >> n >> m >> K;
priority_queue<pair<int,int>> pq;
vector<int> a(n);
vector<int> b(m);
int sum=0;
for (int i = 0; i < n; i++) { cin >> a[i]; sum+=a[i]; }
for (int i = 0; i < m; i++) { cin >> b[i]; }
vector<int> dp(MAXB*m,-1);
dp[0]=0;
for (int i = 0; i < m; i++)
{
for (int j = sz(dp)-1; j >= 0; j--)
{
if(dp[j]==-1) continue;
dp[j+b[i]]=max(dp[j]+min(b[i],n), dp[j+b[i]]);
}
}
int ans=-1;
for (int i = sum; i < sz(dp); i++)
{
if(dp[i]>=K*n){
ans=i-sum;
break;
}
}
if(*min_element(all(a))<K) ans=-1;
if(ans==-1) cout << "Impossible\n";
else cout << ans << "\n";
return 0;
}
