14

#include<stdio.h>
#include<math.h>
int f(int c);
int main(void)
{
	int i,x,c;
	double s,a,b;
	scanf("%d",&x);
	i=1,s=1;
	while(fabs(a)>=0.00001){
	    b=-1;
		a=pow(x,2*i-1);
		i++;
		c=f(c);
		s=s+a*b/c;
		b=-b;		
	}
	printf("%.6f\n",s);
	return 0;
}
int f(int c)
{
	int j,i=1;
	c=1;
	for(j=1;j<=2*i-1;j++)
		c=c*j;
	return c;
}