#include <bits/stdc++.h>
using namespace std;

#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    // freopen("input.txt", "r", stdin);
    long long n, answer;
    answer = 0;
    cin >> n;
    for(long long i = 1; n >= 0; i++) {
        n -= i;
        answer++;
    }
    cout << answer - 1;
    return 0;
}