import sys
from collections import defaultdict, Counter, deque
from itertools import permutations, combinations, product, combinations_with_replacement, groupby, accumulate
import operator
from math import sqrt, gcd, factorial
# from math import isqrt, prod,comb  # python3.8用(notpypy)
#from bisect import bisect_left,bisect_right
#from functools import lru_cache,reduce
#from heapq import heappush,heappop,heapify,heappushpop,heapreplace
#import numpy as np
#import networkx as nx
#from networkx.utils import UnionFind
#from numba import njit, b1, i1, i4, i8, f8
#from scipy.sparse import csr_matrix
#from scipy.sparse.csgraph import shortest_path, floyd_warshall, dijkstra, bellman_ford, johnson, NegativeCycleError
# numba例 @njit(i1(i4[:], i8[:, :]),cache=True) 引数i4配列、i8 2次元配列,戻り値i1
def input(): return sys.stdin.readline().rstrip()
def divceil(n, k): return 1+(n-1)//k  # n/kの切り上げを返す
def yn(hantei, yes='Yes', no='No'): print(yes if hantei else no)


def main():
    mod = 10**9+7
    mod2 = 998244353
    n = int(input())
    ans = [1]*(n+1)
    p=int(n**0.5)+3
    check = [True]*(int(n**0.5)+5)
    for i in range(2, int(n**0.5)+3):
        if check[i]:
            for j in range(i,p,i):
                check[j]=False
            i2=i**2
            for j in range(i**2,n+1,i**2):
                j2=j
                while j2%(i2)==0:
                    j2//=i2
                    ans[j]*=i
    print(sum(ans)*2-n-2)


if __name__ == '__main__':
    main()