#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,i=0,s=0;
	cin>>n;
	while(1){
		i++;
		s+=i;
		if(s>=n){
			break;
		}	
	}
	cout<<i;
	return 0;
}

/**************************************************************
	Problem: 1248
	User: zzz
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/