#include<iostream>
#include<cstdio>
#define endl '\n'
using namespace std;
typedef long long ll;
int i,j,p,q,n,m,k,a;
int main()
{
    freopen("exercise.in", "r", stdin);
    freopen("exercise.out", "w", stdout);
    cin>>n;
    i = 1;
    while(n>0)
    {
        if(n<=0)break;
        n-=i;
        i++;
    }
    cout<<i-1<<endl;
    return 0;
}