import sys, math
input = sys.stdin.readline

r, x1, y1, x2, y2 = [int(c) for c in input().split()]

dX = abs(x2-x1)
dY = abs(y2-y1)
d = (dX**2+dY**2)**(1/2)
move = math.ceil(d/(2*r))

print(move)


	
