import math
def Appel(arr):
    dobleR = arr[0] * 2
    dx = True
    dy = True
    distX = (arr[3] - arr[1])**2
    distY = (arr[4] - arr[2])**2
    distTot = math.sqrt(distX + distY)
    if(arr[3] == arr[1]):
        dx = False
    if(arr[4] == arr[2] ):
        dy = False
    if(dy == False and dx == False):
        return 0
    if(dy or dx):
        result = distTot/dobleR
    return math.ceil(result)
    

arr=[]
arr = list(map(int, input().strip().split()))

print(Appel(arr))