from math import ceil
def dist(a,b):
    return (a*a + b*b)**.5

def how_many(r, sx,sy, tx,ty):
    l = dist(sx-tx,sy-ty)
    #print(l)
    res = (l )/(2*r)
    return ceil(res)

r,sx,sy,tx,ty = map(int, input().split())

print(how_many(r,sx,sy,tx,ty))
