#include<bits/stdc++.h>
using namespace std;
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define dbg(x) cout << #x << '=' << x << '\n';
#define ll long long
#define sz size()
#define x first
#define y second
#define pi pair <int, int>
#define pii pair <int, pi>
#define vi vector <int>
#define nmax 301
const ll mod = 998244353;
int n, m, k, s;
int a[605], b[605], dp[309][100001];
int32_t main(){
ios_base :: sync_with_stdio(0); cin.tie(); cout.tie();
cin>>n>>m>>k;
if(m<k) return cout<<"Impossible", 0;
for(int i=1; i<=n; i++){
cin>>a[i];
s+=a[i];
if(a[i]<k) return cout<<"Impossible", 0;
}
for(int i=0; i<m; i++) cin>>b[i];
for(int i=0; i<=100000; i++){
for(int j=0; j<=m+1; j++) dp[j][i]=-(1<<30);
}
dp[0][0]=0;
for (int i = 0; i<m; i++) {
for (int j = 0; j <= 90000; j++) {
if (dp[i][j] == -(1 << 30)) continue;
dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
dp[i + 1][j + b[i]] = max(dp[i + 1][j + b[i]], dp[i][j] + min(b[i], n));
}
}
for (int i = s; i <= 90000; i++) {
if (dp[m][i] >= n * k) return cout<<i - s, 0;
}
cout<<"Impossible";
}
