#include<stdio.h>

float approx_sqrt(int);

int main() {
	int z;
	scanf("%d", &z);
	printf("%.4f\n", approx_sqrt(z));
	return 0;
}

float approx_sqrt(int z) {
	float appr, ris;
	if(z>0) {
		appr=approx_sqrt(z-1);
		ris=(0.5)*(appr+(z/appr));
		return ris;
	}
	if(z==0) {
		return 1;
	}
}

