output_description: Print the distance in real number. The output should not contain an absolute
  error greater than 10-4.
input_description: Four real numbers x1, y1, x2 and y2 are given in a line.
attempt: a, b, c, d = list(map(float, input().split()))
  print("%.5f" % (((c - a) ** 2 + (b - d) ** 2) ** 0.5))
  
problem_description: Distance
  
    
  
  Write a program which calculates the distance between two points P1(x1, y1)
  and P2(x2, y2).
samples: [{"input": "0 1 1", "output": ".41421356"}]