import math
a = raw_input().split();
r = int(a[0])
x = int(a[1])
y = int(a[2])
x1 = int(a[3])
y1 = int(a[4])
temp = (x-x1)**2 + (y-y1)**2
temp = temp**(0.5);
temp = temp/(2*r);
print int(math.ceil(temp))