import math
a = list(input().split())
r = int(a[0])
x = int(a[1])
y = int(a[2])
p = int(a[3])
q = int(a[4])
sum1=0
k=0
sum1 = math.sqrt((x-p)**2  + (y-q)**2)
r=2*r
while sum1>=r:
    sum1=sum1 - r
    k=k+1
if sum1>=r/2:    
    leng= math.sqrt((sum1)**2 - (r/2)**2)
else:
    leng=0
if sum1==0:
    print(int (k))
else:
    if sum1-(r/2)>leng:
        print(int (k+2))
    else:
        print(int (k+1))