#include
void main()
{
long n=1;
float s=0.0,t=1.0;
while(1.0/n>=0.00001)
{
s=s+t/n;
n=n+3;
t=-t;
}
printf("%.5f\n",s);
}
#include
int main()
{
long n=1;
float s=0.0,t=1.0;
while(n<100000)
{
s=s+t/n;
n=n+3;
t=-t;
}
printf("%7.5f\n",s);
return 0;
}