/*
    Bismillah Hir Rahmanir Rahim
 
    *MAY ALLAH HELP ME*
*/
 
///Containers Start..
#include <iostream>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <cmath>
#include <ctime>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <vector>
#include <utility>
#include <math.h>
#include <algorithm>
///Container End.
 
/// **** So be patient. Indeed, the promise of ALLAH is truth - QURAN - 30:60 ****
 
///Macro Start..
#define PI          acos(-1.0)
#define LL          long long
#define pii         pair <int, int>
#define ppi         pair <pii, int>
#define ff          first
#define ss          second
#define sz(a)       int((a).size())
#define pb          push_back
#define mp          make_pair
#define nn          '\n'
#define all(c)      (c).begin(), (c).end()
 
///Macro End.
 
 
using namespace std;
 
 
 
int main()
{
    /// I May Not Be Able To Solve Today's Problems, But I Will Learn, And Obiviously I Can Solve Every Problems One Day :)
 
    long long int n, sum, total, x;
 
    cin >> n;
 
    x = floor( ( sqrt( 8 * n + 1 )  - 1 ) / 2 );
 
    //cout << x << endl;
 
    total = n - (x * ( x + 1)) / 2;
 
    //cout << total << endl;
 
    if( total == 0 && x > 0  )
    {
        cout << x << endl;
    }
    else if( total == x )
    {
        cout << x << endl;
    }
    else if( x > total )
    {
        cout << total << endl;
    }
 
 
 
    return 0;
}

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