这是我的，没用你那个
# include <stdio.h>
main ()
{
    int x,i,j;
    printf("N=?");
    scanf("%d",&x);
    for (i=2;i<=x;i++)
    {
        for (j=2;j<i;j++)
        {
            if (i%j==0)
                break;
        }
        if (j==i)
            printf("%d\n",i);
    }
}