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#include<bits/stdc++.h>
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using namespace std;
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typedef long long ll;
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const ll N=(1<<16)+10;
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ll t,n,i,j,ans,a[N],p[N],f[N];
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int main(){
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 cin>>t;n=(1<<t)-1;f[0]=1;
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 for(i=1;i<=n;i++)cin>>a[i],p[i]=i;
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 stable_sort(p+1,p+1+n,[](int x,int y){return a[x]<a[y];});
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 for(i=1;i<=n;i++)
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  if(!f[p[i]]){
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   ans+=a[p[i]];
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   for(j=0;j<=n;j++)f[j^p[i]]|=f[j];
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  }
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 cout<<ans;
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}