from math import sqrt

r,x1,y1,x2,y2 = map(int, raw_input().split())
dist = sqrt(abs(x1-x2)*abs(x1-x2) + abs(y1-y2)*abs(y1-y2))
ans = int(dist)/(2*r)
if(ans*2*r == dist):
    print ans
else:
    print ans+1