l=100000
P=[1]*l
P[0]=0
P[1]=0
for i in range(2,l):
  if P[i]:
    for j in range(i+i,l,i):
      P[j]=0
P=[i for i in range(2,l) if P[i]]
n=int(input())
s=0
for p in P:
	a=p*p
	while a<=n:
		s+=a
		a*=p
print(s)