import math
r ,x1,y1,x2,y2 = [int(x) for x in input().split()]
#print(abs(x1-x2)**2)
t = (abs(x1-x2)**2 + abs(y1-y2)**2)
#print(t)
t = math.sqrt(t)
#print(t)
t = t/(2*r)
#print(t)
if t%1==0:
    print(int(t))
else:
    print(int(t)+1)