#include<bits/stdc++.h>
using namespace std;

int64_t div_enum_sum(int64_t n)
{
  int64_t res=0;
  for(int64_t i=1;i*i<=n;++i)
  {
    if(n%i==0)
    {
      res+=i;
      if(i!=n/i)
      {
        res+=n/i;
      }
    }
  }
  return res;
}

int main()
{
  int64_t N;
  cin>>N;
  if(N%2==0)
  {
    N/=2;
  }
  cout<<div_enum_sum(N)<<endl;
}