import math  
def calculateDistance(x1,y1,x2,y2):  
     dist = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)  
     return dist 

r,x,y,x1,y1=map(int,input().split())

if x==x1 and y==y1:
    print(0)
else:
    print(math.ceil(calculateDistance(x,y,x1,y1)/(2*r)))
