using namespace std;

int main() {
    long long n;
    cin >> n;
    
    long long low = 1;
    long long high = 50000;
    long long ans = 0;
    
    while (low <= high) {
        long long mid = (low + high) / 2;
        long long total = mid * (mid + 1) / 2;
        
        if (total <= n) {
            ans = mid;
            low = mid + 1;
        } else {
            high = mid - 1;
        }
    }
    
    cout << ans << endl;
    return 0;
}