import sys
r, x, y, x1, y1 = map(int, input().split())
if x == x1  and  y == y1:
    print(0)
    sys.exit(0)
dist = ( ((x - x1) ** 2) + ((y - y1) ** 2) ) ** 0.5
t = 0
while dist > (r * 2):
    t = t + 1
    dist = dist - (2 * r)
print(t + 1)