ar = []
for i in input().split(' '):
    ar.append(int(i))
r = ar[0] * 2
x1 = ar[1]
y1 = ar[2]
x2 = ar[3]
y2 = ar[4]
diff = pow((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2), 0.5)
count = diff // r
if diff % r != 0:
    count = count + 1
print(int(count))