You are given a paragraph, with numbered sentences, and a question. Write the numbers of the sentences needed to answer the given question. Separate multiple sentence numbers with a comma (", "). E.g. "1, 2" would be the correct response if Sent 1 and Sent 2 are needed to answer the given question (do not include sentences that contain no information that is necessary to answer the question). Sort the sentence numbers in an increasing order (i.e., '1, 2', instead of '2, 1'). Your answer should not contain anything than the sentence numbers separated by a comma (e.g. '1, 2, 3, 4'). The given question requires more than one sentence to answer. So, your answer must contain at least one comma (", ").

Input: Consider Input: Paragraph- Sent 1: Derek was sad.
Sent 2: He was playing in the school yard at recess and a girl in his class was being mean to him.
Sent 3: Her name was Sandy.
Sent 4: Sandy was best friends with Alexis.
Sent 5: Alexis was nice to Derek, but Sandy kept being mean.
Sent 6: Sandy kicked dirt at Derek and called him mean names.
Sent 7: Alexis felt bad that her friend was so nasty to Derek.
Sent 8: Derek knew that Sandy did not like him, so he sat down in the school yard with a big frown.
Sent 9: All of a sudden, a stranger walked up to Derek and asked him if he wanted some rock sugar candy.
Sent 10: He told Derek he had lots of sugar rock candy in his car in the parking lot.
Sent 11: Derek remembered his parents telling him never to talk to strangers, so he started running away from the man.
Sent 12: Sandy and Alexis were on the jungle gym and they saw Derek running from the stranger.
Sent 13: They went to tell their teacher, Mrs. Mustard, who was still inside the classroom.
Sent 14: Sandy and Alexis came into the classroom screaming for help.
Sent 15: Derek ran into the classroom right after the girls.
Sent 16: Mrs. Mustard looked out into the recess yard, but the stranger was gone.
Sent 17: Jenny, Mrs. Mustard's helper, called the police to report what had happened.
Question: What happened with Derek and the stranger?.

Output: 1, 2.

Input: Consider Input: Paragraph- Sent 1: (CNN) -- Federal authorities are investigating threatening letters allegedly containing deadly ricin in Spokane, Washington, the FBI said Thursday.
Sent 2: The FBI and the U.S. Postal Inspection Service are trying to find the source of the two letters, intercepted Tuesday during a screening procedure at a postal facility in Spokane, FBI spokeswoman Ayn Sandalo Dietrich said.
Sent 3: "While we cannot offer further comment on this incident, we stress that law enforcement agencies will continue to assess and address the full spectrum of potential threats," she said.
Sent 4: The American Postal Workers Union was notified of the two suspicious letters by the Postal Service, the union said.
Sent 5: One letter was addressed to the Spokane Post Office and the other to a federal judge in Spokane, the union said.
Sent 6: Both were postmarked May 14, the union said.
Sent 7: Postal Service management told employees they weren't at risk from handling the letters because the suspected substance was not in a form that could be inhaled or readily ingested, the union said.
Sent 8: Preliminary lab tests showed the substance to be ricin, the union said.
Sent 9: The union is monitoring the situation, President Cliff Guffey said.
Sent 10: "Our members' safety is our primary concern," he said in a statement.
Sent 11: In an apparently unrelated case, ricin-tainted letters sent to President Obama and others touched off high anxieties in Washington and elsewhere last month.
Sent 12: James Everett Dutschke, 41, of Tupelo, Mississippi, has been charged with possession and use of a biological agent as a weapon in connection with those letters sent to Obama and others.
Question: The FBI and the U.S. Postal Inspection Service are trying to find the source of the two letters which contained what?.

Output: 1, 2.

Input: Consider Input: Paragraph- Sent 1: While glaciers erode the landscape, they also deposit materials.
Sent 2: Glaciers deposit their sediment when they melt.
Sent 3: They drop and leave behind whatever was once frozen in their ice.
Sent 4: Its usually a mixture of particles and rocks.
Sent 5: It can be of all sizes, called glacial till.
Sent 6: Water from the melting ice may form lakes or other water features.
Sent 7: Figure Moraine is sediment deposited by a glacier.
Sent 8: A ground moraine is a thick layer of sediments left behind by a retreating glacier.
Sent 9: An end moraine is a low ridge of sediments deposited at the end of the glacier.
Sent 10: It marks the greatest distance the glacier advanced.
Sent 11: A drumlin is a long, low hill of sediments deposited by a glacier.
Sent 12: Drumlins often occur in groups.
Sent 13: These groups are called drumlin fields.
Sent 14: The narrow end of each drumlin points in the direction of an advancing glacier.
Sent 15: An esker is a winding ridge of sand deposited by a stream of meltwater.
Sent 16: Such streams flow underneath a retreating glacier.
Sent 17: A kettle lake occurs where a chunk of ice melt as they are left behind as a glacier retreats.
Sent 18: When the huge chuck of ice melts it leaves a depression.
Question: What do glaciers leave behind as they melt?.
Output: 1, 2, 3, 4.