#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
	long long n = 0;
	cin >> n;
	long long rest = sqrt(n * 2);
	if (rest*(rest + 1) / 2 < n) {
		cout << rest + 1;
		return 0;
	}
	cout << rest;
	return 0;
}