What is the running time of the following piece of code ?

for(k=1; k<=n; k*=2)
{
     for(i=0; i<k; i++)
     {
          for(j=0; j<n; j+=2)
               sum=sum+1;
          for(j=1; j<n; j*=2)
               sum=sum+1;
     }
}

Difficulty level
This exercise is mostly suitable for students 
O(n*log(n)^2)
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