PTS C++

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

ll n;

void giai()
{
    for(int k=int(sqrt(2*n));k>=2;k--)
    {
        if(2*n%k==0)
        {
            if((2*n/k-k-1)%2==0)
            {
                cout<<k;
                return;
            }
        }
    }
    cout<<0;

}
int main()
{
    freopen("phantich.inp","r",stdin);
    freopen("phantich.out","w",stdout);
    cin>>n;
    giai();
}