What was Elie's main thought as the men and women were being herded from the train?

The Jews of Sighet do not think a day will come when they will be taken prisoner and subjected to the atrocities they will experience in the camps. They ignore warnings of the impending danger and grow confident in their ability to escape the ordeal based on news that the Red Army is making progress. However, events take a drastic turn after German soldiers arrive in Sighet. The soldiers’ arrival is quickly followed by transportation...

The Jews of Sighet do not think a day will come when they will be taken prisoner and subjected to the atrocities they will experience in the camps. They ignore warnings of the impending danger and grow confident in their ability to escape the ordeal based on news that the Red Army is making progress. However, events take a drastic turn after German soldiers arrive in Sighet. The soldiers’ arrival is quickly followed by transportation of the Jews out of Sighet and into the concentration camps.

When Eliezer and the other prisoners reach Birkenau, they are asked to disembark from the cattle cars, and all that occupies Eliezer's mind is the thought of not losing his father and remaining alone. By this time, the men have already been separated from the women. Elie ensures that he is not separated from his father and lives in constant fear of separation until his father dies in the camps.

My hand tightened its grip on my father. All I could think of was not to lose him. Not to remain alone. The SS officers gave the order. "Form ranks of fives!"