#include <bits/stdc++.h>
#define DIM 310
#define INF 2000000000
using namespace std;
int a[DIM],b[DIM],dp[DIM][DIM*DIM];
int n,m,k,i,j,sum_a,sum_b;
int main (){
cin>>n>>m>>k;
for (i=1;i<=n;i++){
cin>>a[i];
sum_a += a[i];
}
for (i=1;i<=m;i++){
cin>>b[i];
sum_b += b[i];
}
sort (b+1,b+m+1);
/// trb sa am minim k bucatari diferiti pt fiecare masa
/// dp[i][j] - nr maxim de zone pe care pot sa le acopar cu primii i bucatari si in total sa platesc j
for (i=1;i<=m;i++)
for (j=0;j<=sum_b;j++)
dp[i][j] = -INF;
dp[0][0] = 0;
for (i=1;i<=m;i++){
for (j=b[i];j<=sum_b;j++){
if (dp[i-1][j-b[i]] != -INF)
dp[i][j] = max (dp[i-1][j],dp[i-1][j-b[i]]+min(n,b[i]));
else dp[i][j] = dp[i-1][j];
}
}
for (j=sum_a;j<=sum_b;j++){
if (dp[m][j] >= n*k){
cout<<j-sum_a;
return 0;
}
}
cout<<"Impossible";
return 0;
}
