import math
INPUT = input()
INPUT = INPUT.split(' ')
r = int(INPUT[0])
x1 = int(INPUT[1])
y1 = int(INPUT[2])
x2 = int(INPUT[3])
y2 = int(INPUT[4])
r = 2*r
dist = math.sqrt((x1-x2)**2+(y1-y2)**2)
res = dist/r
if res.is_integer():
    print(int(res))
else:
    print(int(res)+1)
    
