I heard this story at a Holocaust Remembrance Day program some years ago and I cannot swear that every detail is accurate, but the story itself is true. The person who told it is a friend who is the son of Holocaust survivors
His father was around 16 years old and the family was locked up in the Warsaw Ghetto with thousands of other Jews and no food. They were on the verge of starvation when the 16 year old decided he had nothing to lose by trying to sneak out of the Ghetto and find some food. If he succeeded, they would have something to eat. If he got killed trying, then they were still no worse off because they were soon going to die of starvation anyway.
My friend's father was gone several hours and came back with exactly one potato -- not much for their family of four, but something.
He triumphantly handed it to his father who proceeded to take a knife, cut the potato in half, and head for the door of the family's apartment.
"Dad, what are you doing?"
"The people downstairs are hungry too."