//#pragma GCC target ("avx2")
//#pragma GCC optimize ("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define F first
#define S second
#define pb push_back
const int N = 1e6+100, NN=26, mod=1e9+7;
int dp[N];
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, m, k;
cin >> n >> m >> k;
int a[n + 1], b[m + 1], sum=0, sum2=0;
bool b2=0;
for(int i = 1 ; i <= n ; ++i) {
cin >> a[i];
sum2+=a[i];
if(a[i]<k) b2=1;
}
if(b2 == 1 || k > m) {
cout << "Impossible";
return 0;
}
for(int i = 1 ; i <= sum ; ++i) dp[i] = -1e18;
for(int i = 1 ; i <= m ; ++i){
cin >> b[i];
sum+=b[i];
}
for(int i = 1 ; i <= m ; ++i) {
for(int j = sum-b[i]; j >= 0; --j) {
if(dp[j]!=-1e18) dp[j + b[i]] = max(dp[j + b[i]], dp[j] + min(n, b[i]));
}
}
int ans=1e18;
for(int i = sum2 ; i <= sum ; ++i) {
if(dp[i]>=n*k){
ans=i;
break;
}
}
if(ans==1e18) cout << "Impossible";
else cout << ans-sum2;
}
