#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;
const double gen2 = sqrt(2);

int main() {
    ll need;
    cin >> need;
    need++;
    ll n = 0;
    while (4*n*n<need) {
        n++;
    }
        if((n*n-1)*4>=need) {
            printf("%llf\n", sqrt((n - 1) * (n - 1) + n * n));
        }else {
            printf("%llf\n", n * gen2);
        }
}