void shell(char *v[], int n)
{	  /* sort v[0]...v[n-1] into increasing order */
    int gap, i, j;
	char *temp;

    for (gap = n/2; gap > 0; gap /= 2)
        for (i = gap; i < n; i++)
            for (j=i-gap; j>=0 && strcmp(v[j],v[j+gap])>0; j-=gap) {
                temp = v[j];
                v[j] = v[j+gap];
                v[j+gap] = temp;
            }
}