#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>
const int mxn = 303;
const int mxc = mxn*mxn;
int N,M,K,arr[mxn],dp[mxc],brr[mxn];
int main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>N>>M>>K;
int sum = 0;
for(int i = 0;i<N;i++)cin>>arr[i],sum += arr[i];
for(int i = 0;i<M;i++)cin>>brr[i];
for(int i = 0;i<N;i++){
if(arr[i]<K){
cout<<"Impossible";
return 0;
}
}
memset(dp,-1,sizeof(dp));
dp[0] = 0;
for(int i = 0;i<M;i++){
for(int j = mxc-1;j>=brr[i];j--){
if(dp[j-brr[i]] != -1)dp[j] = max(dp[j],dp[j-brr[i]]+min(brr[i],N));
}
}
for(int i = sum;i<mxc;i++){
if(dp[i]>=N*K){
cout<<i-sum;
return 0;
}
}
cout<<"Impossible";
return 0;
}
