import string

#brute force
def stupid_geometry(r,x,y,x1,y1):
    d = ((x1-x)**2 + (y1-y)**2)**0.5
    if d<r:
        return 0
    if d%r==0:
        return int((d // r) - 1)
    else:
        return int((d // r))



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










