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#include <bits/stdc++.h>
using namespace std ;
#include <algorithm>
#define int long long 
void solve ()
{
int n,k;cin>>n>>k;
int a[n],b[n];
int idx1=0,idx2=0,
for(int i = 0; i<n;i++) cin>>a[i];
for(int i = 0; i<n;i++)cin>>b[i];
int m1,m2; m1 = a[(n/2)-1];m2 = a[n/2];
for(int i = 0; i<n;i++)
    if(b[i] == 1)
        a[i] += k;
int x = a[0],y=a[n-1];
for(int i = 0; i<n-2;i++)
    if(x < a[i])
    {
        x = a[i];
        idx1 =i;
    }
for(int i = n/2 ; i < n; i++) 
    if(y < a[i])
    {
        y = a[i];
        idx2 = i;
    }
int max1 = m1+y; int max2 =m2+x;
if(b[(n/2)-1] ==1 &&b[idx2] ==1) max2-= k;
if(b[(n/2)] == 1 && b[idx1] ==1) max1 -= k;
cout << max(max1,max2) << endl;
 
}
signed main ()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
// cin>>t;
// while(t--)
// { 
    solve();
// } 
    return 0;    
}