the conspiracy was committed as alleged, and that Leyvas participated throughout the conspiracy.  Leyvas did not contend on his original appeal, and except for his point as to the necessity of showing an overt act, does not now contend, that there is no substantial evidence to support the implicit jury finding that the conspiracy continued until November 21, 1956, and that he participated in it throughout.


12
We therefore hold that the July 18, 1956 amendment of 21 U.S.C. 174, increasing the mandatory imprisonment for first offenders from two years to five years, is applicable to Leyvas' conviction on count 17.  It follows that the district court was obliged to sentence Leyvas to imprisonment for at least five years on count 17.  The reduction in the originalfive-year sentence to give Leyvas credit for serving nineteen months in jail after he had filed an election pursuant to Rule 38(a)(2), Federal Rules of Criminal Procedure, was therefore void.  Accordingly, the district court was required to set aside that void order and reinstate the original five-year sentence.


13
However, neither the 1956 enactment nor any other statute which has been called to our attention required the trial court to make the mandatory five-year sentence on count 17 consecutive to the sentence imposed on the other counts.  Thus, instead of impermissibly reducing the five-year sentence on count 17 to give Leyvas credit for the nineteen months he served in jail pending disposition of his appeal, the court could have made the originally-imposed five-year sentence on that count concurrent,