#include <stdio.h>

int main()
{
	double sum=0,tmp=1;
	/*while((1/tmp)>=1e-6){
		sum+=1/tmp;
		sum-=1/(tmp+2);
		tmp+=4;
		printf("%.15f\n",1/(tmp+2));
	}
	printf("%.15f",4*sum);*/
	printf("%.15f\n",0.123e-6);
	return 0;
}