def search(matrix,value):
   sizex = len(matrix[0])-1
   sizey = len(matrix)-1
   initialx = sizex
   initialy = 0
   while initialx >= 0 and initialy <= sizey:
      if matrix[initialy][initialx] == value:
         return initialx,initialy
      elif  matrix[initialy][initialx] > value:
         initialx -= 1
      elif matrix[initialy][initialx] <= value:
         initialy += 1
      else:
         return -1,-1
   return -1,-1

M = [ [  1,  5,  7,  9 ],  
    [  4,  6, 10, 15 ],  
    [  8, 11, 12, 19 ],  
    [ 14, 16, 18, 21 ] ]  
value = 12
print(search(M,value))
value = 17
print(search(M,value))