#include <iostream>
using namespace std;

int main() {
    long long N;
    cin >> N;
    long long left = 0, right = N, ans = 0;
    while (left <= right) {
        long long mid = left + (right - left) / 2;
        if (mid <= N / mid) { // tránh tràn số
            ans = mid;
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    cout << ans << endl;
    return 0;
}