import math

def get_int_vector():
    return [int(x) for x in input().split()]

r, x0, y0, x, y = get_int_vector()

dist = math.sqrt((x0-x)**2 + (y0-y)**2)
steps = int(dist//(2*r))
#print(steps, dist)
if dist - steps*2*r > 0:
    steps += 1

print(steps)

