#include<stdio.h>
#include<math.h>
double fun(double x)
{
??? int i;
?? double s[]={0},sum;
?? sum=s[0]=1;
??
?? for(i=1;fabs(s[i])>=0.000001;i++)
?? {
?????? s[i]=(0.5-i+1)*x/i*s[i-1];
?????? sum+=s[i];
?? }
?? return sum;

}
int main()
{
??? double x,s;
??? printf("Input x:\n");
??? printf("0.21\n");
??? s=fun(0.21);
??? printf("s=%f\n",s);
}