#include<bits/stdc++.h>
using namespace std;
int main()
{
	int i=1,n,s=0,j=1;
	cin>>n;
	while(s!=n){
		for(j=1;j<=i;j++)
			s++;
		i++;
	}
	cout<<i-1;
	return 0;
}
/**************************************************************
	Problem: 1248
	User: houshanglin
	Language: C++
	Result: Time Limit Exceed
****************************************************************/