What follows is an opinion from a United States Court of Appeals.
Intervenors who participated as parties at the courts of appeals should be counted as either appellants or respondents when it can be determined whose position they supported. For example, if there were two plaintiffs who lost in district court, appealed, and were joined by four intervenors who also asked the court of appeals to reverse the district court, the number of appellants should be coded as six.
When coding the detailed nature of participants, use your personal knowledge about the participants, if you are completely confident of the accuracy of your knowledge, even if the specific information is not in the opinion. For example, if "IBM" is listed as the appellant it could be classified as "clearly national or international in scope" even if the opinion did not indicate the scope of the business. 

Your task concerns the first listed appellant. The nature of this litigant falls into the category "federal government (including DC)", specifically "other, not listed, not able to classify". Your task is to determine which specific federal government agency best describes this litigant.

Opinion:
UNITED STATES of America, Appellant and CrossAppellee, v. MASSACHUSETTS TRUSTEES OF EASTERN GAS AND FUEL ASSOCIATES, MYSTIC STEAMSHIP DIVISION, Appellee and Cross-Appellant.
No. 9533.
United States Court of Appeals Fourth Circuit
Argued Nov. 12, 1964.
Decided Feb. 1, 1965.
Alan Raywid, Atty., Dept, of Justice (John W. Douglas, Asst. Atty. Gen., Morton Hollander and Lawrence F. Ledebur, Attys., Dept, of Justice, and Claude V. Spratley, Jr., Norfolk, Va., on brief), for appellant and cross-appellee.
R. M. Hughes, III, and Charles R. Dalton, Jr., Norfolk, Va. (Seawell, McCoy, Winston & Dalton, Norfolk, Va., on brief), for appellee and cross-appellant.
Before SOBELOFF, Chief Judge, and HAYNSWORTH and J. SPENCER BELL, Circuit Judges.
PER CURIAM.
This is an appeal and a protective cross-appeal from decrees entered by the district court in consolidated admiralty actions arising out of a ship collision in international waters off the Virginia coast. The opinion of the district court is reported at 224 F.Supp. 705 (E.D.Va. 1963). In that opinion, the district court carefully analyzed the evidence and found the facts. We think its factual findings are fully supported by substantial evidence in the record. Further, we think the court below correctly applied the pertinent law. Since the district court opinion fully discusses and we think properly applies the precedents to the issues raised on this appeal, we see nothing to be gained from further elaboration. The decrees are
Affirmed.

Question: This question concerns the first listed appellant. The nature of this litigant falls into the category "federal government (including DC)", specifically "other, not listed, not able to classify". Which specific federal government agency best describes this litigant?

Choices:
United States - in corporate capacity (i.e., as representative of "the people") - in criminal cases
United States - in corporate capacity - civil cases
special wartime agency
Other unlisted federal agency (includes the President of the US)
Unclear or nature not ascertainable

Answer: 0