The man and the chicken cross the river, (the fox and corn are safe together), he leaves the chicken on the other side and goes back across.
The man then takes the fox across the river, and since he can’t leave the fox and chicken together, he brings the chicken back.
Again, since the chicken and corn can’t be left together, he leaves the chicken and he takes the corn across and leaves it with the fox.
He then returns to pick up the chicken and heads across the river one last time.