#line 1 "main.cpp"
#include <iostream>

using namespace std;
using lint = long long;

void solve() {
    lint n;
    cin >> n;

    lint ok = 100000, ng = 0;
    while (ok - ng > 1) {
        auto mid = (ok + ng) / 2;

        if (mid * (mid + 1) / 2 >= n) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    cout << ok << "\n";
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();

    return 0;
}