from math import sqrt
r,x,y,x1,y1 = [long(x) for x in raw_input().split(' ')]
dist = (x - x1)**2 + (y - y1)**2
dist = dist**0.5
steps = dist/(r*2)

if steps == long(steps) :
    steps = long(steps)
else :  
    steps = long(steps) + 1

print steps
