#include <math.h>

/* compute the length for one dimension*/
int length(int N, int i, double *scf, double *ap, double D, int Nvari)
{
  int maxfactor(int n);
  double temp1, temp2;
  int n, j, k, nmax;
  int nlimit = 13;
 
  if (N == 1) {
      n = 1;
    } else {
      
      for (k = 0; k < Nvari; k++) {
	temp1 = fabs(ap[9*k+i])*scf[3*k]*scf[3*k];
	for (j = 1; j <3; j++) {
	  temp2 = fabs(ap[9*k+3*j+i])*scf[3*k+j]*scf[3*k+j];
	  if (temp2 > temp1) 
	    temp1 = temp2;
	}
      }
      temp1 = sqrt(temp1);
      temp1 /= (double)D;
      if ((double)N/temp1 < 2.) {
	n = N+(int)(2*temp1);
      } else {
	n = N+(int)temp1;
      }
      if ((n % 2) != 0) 
	n = n+1;
      nmax = maxfactor(n);
      while (nmax > nlimit) {
	n += 2;
	nmax = maxfactor(n);
      }
    }
  return (n);
}