void ishl(p,n)
  int n,p[];
  { int k,j,i,t;
    k=n/2;
    while (k>0)
      { for (j=k; j<=n-1; j++)
          { t=p[j]; i=j-k;
            while ((i>=0)&&(p[i]>t))
              { p[i+k]=p[i]; i=i-k;}
            p[i+k]=t;
          }
        k=k/2;
      }
    return;
  }