title: Split up a number as the sum of two powers
body: <p>x is my input. 
  I need to find i,j>=0 and  n,m>1 such as <code>x = i**m+j**n</code></p>
  
  <p>For now I have been doing this , but it is way to slow !! How can I improve it ? </p>
  
  <pre><code>from math import sqrt
  import numpy as np
  
  def check(x):
      for i in range(1,int(np.ceil(sqrt(x)))):
          for j in range(1,int(np.ceil(sqrt(x)))):
              for m in range(2,x/2+1):
                  for n in range(2,x/2+1):
                      if((pow(i,m) +pow(j,n))==x):
                          print 'Yes';
                          return ;
      print 'No';
  </code></pre>
  
  <p>thank you ! </p>