r, x, y, _x, _y = map(int, raw_input().split())
from math import sqrt
dist = sqrt((x-_x)**2 + (y-_y)**2)
dec = dist - int(dist)
r = 2*r
dist = int(dist)
steps = dist/r
if dist %r != 0 or dec > 0:
    print steps+1
else:
    print steps