import math
line = map(int, raw_input().split())
r = line[0]
d = 2 * r
x1 = line[1]
y1 = line[2]
x2 = line[3]
y2 = line[4]
d2 = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)
tester = round(math.sqrt(d2))
if (tester == 0): print 0
elif (d2 % tester == 0):
    if (d2 % d == 0): print int(tester / d)
    else: print int(tester / d + 1)
else:
    print int(round(math.sqrt(d2) / d) + 1)
