import math
string = input()
arr = string.split()       
r = int(arr[0]) ; x = int(arr[1]) ; y = int(arr[2]) ; _x = int(arr[3]) ; _y = int(arr[4])
deltaX = math.fabs(x - _x) ; deltaY = math.fabs(y - _y)
steps = math.ceil(math.sqrt((deltaX * deltaX + deltaY * deltaY)) / (2*r))
print (steps)