R=range
L=9**4
P=[]
C=[0]*L
for i in R(2,L):
	if C[i]<1:
		P+=[i];j=i*i
		while j<L:C[j],j=1,j+i
E={}
def e(n):
	if n in E:return E[n]
	a=m=n
	for p in P:
		c=0
		while n%p<1:n//=p;c+=1
		if c:a=a//p*(p-1)
	if n>1:a=a//n*(n-1)
	E[m]=a
	return a
F={1:0}
def f(n):
	if n in F:return F[n]
	D=[1];m=n
	for p in P:
		c=0
		while n%p<1:n//=p;c+=1
		r=len(D)
		for i in R(c):D+=[d*p for d in D[-r:]]
	r=len(D)
	if n>1:D+=[d*n for d in D[-r:]];r*=2
	F[m]=(m+sum(f(m/D[d])*e(D[d])for d in R(1,r)))/(m-1)
	return F[m]
print(f(int(input())))