#include <iostream>

#include <cmath>

using namespace std;

int main(int argc, char** argv) {

long long a,b,c,d,e,h,v;

cin>>a;

  if(a<=1)return 0;

c=0;

p0:  d=2;

p1: if(a%d!=0){

e=3;

h=sqrt(d);

v=sqrt(a);

p2: d++;

p3: if(e!=3&&d%e==0)goto p2;

e++;

if(e<=h&&d<=v) goto p3;

goto p1;  }

b=a/d;

c=c+d;

if(b==1)goto p4;

a=b;

goto p0;

p4: cout<<c<<endl; }