def rotations(r,x,y,a,b):
    dist = ((x-a)**2+(y-b)**2)**(0.5)
    i = 0
    while dist>0:
        dist -= 2*r
        i += 1
    return i
 
A = list(map(int,input().split(" ")))
print(rotations(A[0],A[1],A[2],A[3],A[4]))
