import math

inp = input().split(" ")

rad = int(inp[0])
x1 = int(inp[1])
y1 = int(inp[2])
x2 = int(inp[3])
y2 = int(inp[4])

x = (x1-x2)**2
y = (y1-y2)**2

leng = (x+y)**.5

temp = leng - (rad*2)

res = leng/(rad*2)

print(math.ceil(res))
