#include <iostream.h>
#include <math.h>
void main()
{
    unsigned long n,p,aa,nn;
    cin >> n; nn=2*n;
    for(p=floor((1+sqrt(1+4*n))/2); p>0; p--)
        if(nn%p==0)
        {
            aa=nn/p+1-p;
            if(aa>=0 && aa%2==0)
            {
                cout << aa/2 << ' ' << p << endl;
                break;
            }
        }
}

> #include <iostream.h>
> #include <math.h>
> void main()
> {
>     unsigned long n,p,aa,nn;
>     cin >> n; nn=2*n;
>     for(p=floor((1+>>>>sqrt<<<<(1+4*n))/2); p>0; p--)
>         if(nn%p==0)
>         {
>             aa=nn/p+1-p;
>             if(aa>=0 && aa%2==0)
>             {
>                 cout << aa/2 << ' ' << p << endl;
>                 break;
>             }
>         }
> }

Here is your solution, little modified.

#include <iostream>
#include <math.h>
using namespace std;
void main()
{
unsigned long n,p,aa,nn;
cin >> n; nn=2*n;
for(p=floor((1+sqrt((double)(4*n+1)))/2); p>0; p--)
if(nn%p==0)
{
aa=nn/p+1-p;
if(aa>=0 && aa%2==0)
{
cout << aa/2 << ' ' << p << endl;
break;
}
}
}

Compiling, but WA #2