#include <iostream>

using namespace std;

int main()
{
    int x;
    cin >> x;

    int brojac = 0;
    for(int i = 1; i <= 10000; i += 1) {
        if(i * i < x) {
            brojac += 1;
        }
    }
    cout << brojac << endl;
    return 0;
}