r, x1, y1, x2, y2 = [int(x) for x in input().split()]

distance = ((x2-x1)**2 + (y2-y1)**2)**0.5   # pythagorean theorem

# if the moves made are fractions bigger, that is like if it was exactly the same
# However if it was smaller by a fraction 2.8 for example, that means we have to move to the next number 3
result = int(distance / (2*r)) if distance/(2*r) == int(distance/(2*r)) else int(distance / (2*r))+1    # it's d/2r instead of d/r cause we're moving from the center of the circle to the center of another

print (result)
