#include <bits/stdc++.h>
using namespace std;
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")
#define pb push_back
#define ll long long
#define all(v) v.begin(),v.end()
int mod = 1e8;
const int N = 1e6;
const int inf = 2e9;
int was[2000 + 1][2000 + 1];
signed main(){
//freopen("shuffle.in", "r", stdin);
//freopen("shuffle.out", "w", stdout);
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];
multiset <int> mt;
for(int i = 1; i <= n; i++) cin >> a[i];
for(int i = 1; i <= m; i++){
cin >> b[i];
}
if(m < k){
cout << "Impossible";
return 0;
}
sort(b + 1,b + 1 + m);
for(int i = 1; i <= n; i++){
if(a[i] < k){
cout << "Impossible";
return 0;
}
for(int j = m; j > m - k; j--){
if(b[j] <= 0){
cout << "Impossible";
return 0;
}
b[j]--;
}
a[i] -= k;
sort(b + 1,b + 1 + m);
}
int sum = 0,sum1 = 0;
for(int i = 1; i <= m; i++) sum += b[i];
for(int i = 1; i <= n; i++) sum1 += a[i];
if(sum < sum1){
cout << "Impossible";
return 0;
}
else cout << abs(sum1 - sum);
}
