import math  
def calculateDistance(x1,y1,x2,y2):  
    dist = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)  
    return dist  
def solve(r,x1,y1,x2,y2):
    x=calculateDistance(x1,y1,x2,y2)
    y=math.ceil(x/(2*r))
    print(y)

R,X1,Y1,X2,Y2=[int(x) for x in input().split()]
solve(R,X1,Y1,X2,Y2);
