#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;

int n, ans;

int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        if (n > i*(i-1) / 2 && n <= i*(i+1)/2)
        {
            ans = i;
            break;
        }
    }
    cout << ans;
    return 0;
}
