The "Fox, Chicken, and Grain" is a classic river crossing puzzle. In this scenario, a farmer needs to transport a fox, a chicken, and a bag of grain across a river using a small boat. However, the boat can only carry the farmer and one item at a time. The challenge arises because if the farmer leaves the fox alone with the chicken, the fox will eat the chicken. Similarly, if the chicken is left alone with the grain, it will eat the grain. The goal is to find a way to get all three across the river safely.