import bisect import copy import decimal import fractions import heapq import itertools import math import random import sys import time from collections import Counter,deque,defaultdict from functools import lru_cache,reduce from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max def _heappush_max(heap,item): heap.append(item) heapq._siftdown_max(heap, 0, len(heap)-1) def _heappushpop_max(heap, item): if heap and item < heap[0]: item, heap[0] = heap[0], item heapq._siftup_max(heap, 0) return item from math import gcd as GCD read=sys.stdin.read readline=sys.stdin.readline readlines=sys.stdin.readlines write=sys.stdout.write class Prime: def __init__(self,N): assert N<=10**8 self.smallest_prime_factor=[None]*(N+1) for i in range(2,N+1,2): self.smallest_prime_factor[i]=2 n=int(N**.5)+1 for p in range(3,n,2): if self.smallest_prime_factor[p]==None: self.smallest_prime_factor[p]=p for i in range(p**2,N+1,2*p): if self.smallest_prime_factor[i]==None: self.smallest_prime_factor[i]=p for p in range(n,N+1): if self.smallest_prime_factor[p]==None: self.smallest_prime_factor[p]=p self.primes=[p for p in range(N+1) if p==self.smallest_prime_factor[p]] def Factorize(self,N): assert N>=1 factors=defaultdict(int) if N<=len(self.smallest_prime_factor)-1: while N!=1: factors[self.smallest_prime_factor[N]]+=1 N//=self.smallest_prime_factor[N] else: for p in self.primes: while N%p==0: N//=p factors[p]+=1 if N0 divisors=[1] for p,e in self.Factorize(N).items(): pow_p=[1] for _ in range(e): pow_p.append(pow_p[-1]*p) divisors=[i*j for i in divisors for j in pow_p] return divisors def Is_Prime(self,N): return N==self.smallest_prime_factor[N] def Totient(self,N): for p in self.Factorize(N).keys(): N*=p-1 N//=p return N def Mebius(self,N): fact=self.Factorize(N) for e in fact.values(): if e>=2: return 0 else: if len(fact)%2==0: return 1 else: return -1 N=int(readline()) P=Prime(N) ans=sum(P.primes) print(ans)