#include <stdio.h>
#include <math.h>  
#define N 20
#define M 8 
float r_real[M],r_image[M];

main()
{
    int i,k,mode=1;
    float x_real[N],x_image[N],sum_real=0.0,sum_image=0.0;

    for(i=0;i<N;i++)
    {
        x_real[i]=1.0;
        x_image[i]=0.0;
    }

    for(i=0;i<M;i++)
    {
        sum_real=0.0;
        sum_image=0.0;

        for (k=0;k<N-i;k++)
        {
            sum_real  += x_real[k]*x_real[k+i]-x_image[k]*x_image[k+i];
            sum_image += x_real[k]*x_image[k+i]+x_image[k]*x_real[k+i];
        }
        if (mode==0)
        {
            r_real[i]  = sum_real/k;   
            r_image[i] = sum_image/(N-i);
        }
        else
        {
            r_real[i]  = sum_real/N;
            r_image[i] = sum_image/N;
        }
    }
    for(i=0;i<M;i++)
    printf("r_real[%d]=%f\t\tr_image[%d]=%f\n",i,r_real[i],i,r_image[i]);
}