There was a guy who had a Fox, a Chicken, and a bag of Grain. He
had to cross a river to get back home, but he could only take one
item with him at a time. He could only take the fox, or the grain,
or the chicken. Well, if you leave a chicken and a fox on one side
of the river while taking the bag of grain across, the fox will
eat the chicken, same thing with the chicken and the grain. Can't
leave those two alone or the chicken will eat the grain. How do
you get them all across the river safely?
Take the chicken across first and leave it on the other side (fox doesn't eat the grain). Come back and take either of the other two across, drop it and return
with
the chicken. Leave the chicken on the original bank, and take the remaining item to the other side. With the fox and the grain safely across, return to fetch the chicken.