#include<bits/stdc++.h>
#define int long long
#define task "bbd"
#define ii pair<int,int>
#define iii pair<int,ii>
#define iv pair<ii,ii>
#define se second
#define fi first
#define ffi fi.fi
#define sfi se.fi
#define sse se.se
#define fse fi.se
#define lt(i, c, d) for(int i = c; i <= d; ++i)
#define fl(i, c, d) for(int i = d; i >= c; --i)
#define pb push_back
#define emb emplace_back
#define emf emplace_front
#define em emplace
using namespace std;
const int N=3e2+5,lg=20,mod=1e9+7;
int a[N],m,n,k,ans,b[N],dp[N][N*N],sum,s;
main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
// freopen(task".inp","r",stdin);
// freopen(task"a.out","w",stdout);
cin >> n >> m >> k;
for(int i=1;i<=n;++i){
cin >> a[i];
if(a[i]<k){
cout <<"Impossible";
return 0;
}
s+=a[i];
}
for(int i=1;i<=m;++i){
cin >> b[i];
sum+=b[i];
}
memset(dp,-0x3f,sizeof dp);
dp[0][0]=0;
for(int i=1;i<=m;++i){
for(int j=0;j<=sum;++j){
dp[i][j]=dp[i-1][j];
if(j>=b[i])dp[i][j]=max(dp[i][j],dp[i-1][j-b[i]]+min(b[i],n));
}
}
for(int j=s;j<=sum;++j){
if(dp[m][j]>=n*k){
cout <<j-s;return 0;
}
}
cout<<"Impossible";
}
