
import sys
def get_ints(): return list(map(int, sys.stdin.readline().strip().split()))
import math
arr = get_ints()

r = arr[0]
x1 = arr[1]
y1 = arr[2]
x2 = arr[3]
y2 = arr[4]
diff = math.sqrt((y2 - y1)*(y2 - y1) + (x2 - x1) * (x2 - x1))
print(math.ceil(diff/(2*r)))


