#include <bits/stdc++.h>
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: yangjunwen
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/