#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
const int N = 1e5 + 5, M = 1e4 + 5, mod = 7;

int main()
{
    ll need;
    cin >> need;
    need++;
    ll n = 0;
    while (4 * n * n < need)
    {
        n++;
    }
    if ((n * n - 1) * 4 >= need)
    {
        printf("%.10llf\n", sqrt((n - 1) * (n - 1) + n * n));
    }
    else
    {
        printf("%.10llf\n", n * sqrt(2));
    }
}