#include <bits/stdc++.h>
using namespace std;
#define MAXN 301
#define int long long
int n,m,k;
int a[MAXN],b[MAXN];
int dp[MAXN*MAXN];
int32_t main()
{
cin>>n>>m>>k;
for (int i=1;i<=n;i++) cin>>a[i];
for (int i=1;i<=m;i++) cin>>b[i];
int suma=0;for (int i=1;i<=n;i++) suma+=a[i];
int sumb=0;for (int i=1;i<=m;i++) sumb+=b[i];
if (k>m) {cout<<"Impossible"<<endl;return 0;}
for (int i=1;i<=n;i++)
{
if (a[i]<k) {cout<<"Impossible"<<endl;return 0;}
}
dp[0]=0;for (int i=1;i<=sumb;i++) dp[i]=-INT_MAX;
for (int i=1;i<=m;i++)
{
for (int val=sumb-b[i];val>=0;val--)
{
if (dp[val]==-INT_MAX) continue;
dp[val+b[i]]=max(dp[val+b[i]],dp[val]+min(b[i],n));
}
}
int answer=INT_MAX;
for (int val=suma;val<=sumb;val++)
{
if (dp[val]>=n*k) {answer=val-suma;break;}
}
if (answer==INT_MAX) cout<<"Impossible"<<endl;
else cout<<answer<<endl;
return 0;
}
