#include <iostream>
#include <math.h>
#define n 28123
using namespace std;
int main()
{
int i=0,j=0;
int num = n;
int cntr =0;
int c =0;
unsigned long int sum1=0,suma=0;
int numa[2*n+1]={1};
long int ab[n]={0},abun[n+1]={0};
for(i=1;i<=num;i++)
{
for(j=1;j<i;j++)
{
if((i%j)==0)
{
sum1= sum1+j;
}
}
ab[i]=sum1;
//printf("%ld-->",sum1);
//printf("%d\n",i);
sum1=0;
num=n;
}
for(i=1;i<=num;i++)
for(j=1;j<=num;j++)
{
if((j==ab[i])&&(i<j))
{
//cout<<j<<" "<<i<<endl;
abun[cntr]=i;
cntr++;
}
}
for(i=0;i<2*n+1;i++)
{
numa[i]=1;
}
c=cntr;
//cout<<c<<endl;
for(i=0;i<c;i++)
{
//cout<<i<<": numa["<<abun[i]<<"]="<<numa[abun[i]]<<"\t";
numa[abun[i]]=0;
//cout<<"numa["<<abun[i]<<"]="<<numa[abun[i]]<<endl;
}
for(i=0;i<=c;i++)
{
for(j=i;j<=c;j++)
{
suma = abun[i]+abun[j];
//if(suma>n)
// break;
if(suma==1005)
cout<<suma<<"\t"<<abun[i]<<"+"<<abun[j]<<endl;
//cout<<"numa["<<suma<<"]="<<numa[suma]<<"\t";
numa[suma]=0;
//cout<<"numa["<<suma<<"]="<<numa[suma]<<endl;
suma=0;
}
}
for(i=1;i<=n;i++)
{
if(numa[i]!=0)
{
cout<<i<<" "<<numa[i]<<endl;
suma=suma+i;
}
if(suma==4179871)
{
cout<<i<<endl;
break;
}
}
cout<<suma;
return 0;
}