#include <bits/stdc++.h>
#define DIM 310
#define INF 2000000000
using namespace std;
int a[DIM],b[DIM],dp[2][DIM*DIM];
int n,m,k,i,j,sum_a,sum_b,t,ok;
int main (){
cin>>n>>m>>k;
for (i=1;i<=n;i++){
cin>>a[i];
if (a[i] < k)
ok = 1;
sum_a += a[i];
}
for (i=1;i<=m;i++){
cin>>b[i];
sum_b += b[i];
}
if (ok || sum_b < sum_a){
cout<<"Impossible";
return 0;
}
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 (j=0;j<=sum_b;j++)
dp[0][j] = -INF;
dp[0][0] = 0;
t = 1;
for (i=1;i<=m;i++){
for (j=0;j<=sum_b;j++)
dp[t][j] = -INF;
for (j=0;j<=sum_b;j++){
if (j < b[i]){
dp[t][j] = dp[1-t][j];
continue;
}
if (dp[1-t][j-b[i]] != -INF)
dp[t][j] = max (dp[1-t][j],dp[1-t][j-b[i]] + min(n,b[i]));
else dp[t][j] = dp[1-t][j];
}
t = 1-t;
}
for (j=sum_a;j<=sum_b;j++){
if (dp[1-t][j] >= n*k){
cout<<j-sum_a;
return 0;
}
}
cout<<"Impossible";
return 0;
}
