# Task
 Four men, `a, b, c and d` are standing in a line, one behind another. 
 There's a wall between the first three people (a, b and c) and the last one (d).
 a, b and c are lined up in order of height, so that person a can see the backs of b and c, person b can see the back of c, and c can see just the wall.
 There are 4 hats, 2 black and 2 white. Each person is given a hat. None of them can see their own hat, but person a can see the hats of b and c, while person b can see the hat of person c. Neither c nor d can see any hats.
 Once a person figures out their hat's color, they shouts it. 
 ![](http://stuffbox.in/wp-content/uploads/2016/08/Guess-hat-colour-604x270.png)
 Your task is to return the person who will guess their hat first. You can assume that they will speak only when they reach a correct conclusion.
# Input/Output
 - `[input]` string `a`
  a's hat color ("white" or "black").
 - `[input]` string `b`
  b's hat color ("white" or "black").
 - `[input]` string `c`
  c's hat color ("white" or "black").
 - `[input]` string `d`
  d's hat color ("white" or "black").
 - `[output]` an integer
 The person to guess his hat's color first, `1 for a, 2 for b, 3 for c and 4 for d`.
def guess_hat_color(a,b,c,d):
    return int(b!=c)+1
def guess_hat_color(a,b,c,d):
    return int(b!=c)+1