import math
N = int(input())
M = math.sqrt(N)
M = int(M) + 1
A = [True for i in range(M+1)]
ans = 0
for i in range(2,M+1):
  count = 0
  X = i
  if A[i]:
    while True:
      X *= i
      if X <= N:
        ans += X
      else:
        break
  for j in range(2*i,M+1,i):
    A[j] = False
print(ans)