#include <iostream>
using namespace std;
 
int main(){ 
    int n,s=0,i=0;
    cin>>n;
    
    while(s<n){
    	i++;
    	s+=i;	
	}
	cout<<i<<endl;
}
/**************************************************************
	Problem: 1248
	User: admin
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/