Sum Triunghiular

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

void tri(unsigned long long n)
{
    unordered_set<unsigned long long> tri;
    unsigned long long i=1;
    while(1)
    {
        unsigned long long x=i*(i+1)/2;
        if(x>=n)
            break;
        tri.insert(x);
        i++;
    }
    for(auto tm : tri)
        if(tri.find(n-tm)!=tri.end())
        {
            cout<<n-tm<<" "<<tm;
            exit(0);
        }
    cout<<"NU";
    exit(0);
}

int main()
{
    unsigned long long n;
    cin>>n;
    tri(n);
}