438. Two children are rowing to the other shore. One of them gets out, and the other returns. A soldier ferries across, gets out, and the boy returns. Thus, to ferry one adult across, the boat has to make 4 trips from shore to shore. Therefore, it had to make \(4 \times 358=1432\) trips to ferry the officer and 357 soldiers, and in the end, the boat was back with the children.
438. Escape across the river. During the flight of the Turkish troops at Treise, a small detachment found itself on the bank of a wide and deep river. Here they found a boat in which two boys were boating. The boat was so small that it could only hold two children or one adult.

How did the officer manage to cross the river with his 357 soldiers, returning the boat to the boys at the end of the crossing? How many times did the boat have to cross from bank to bank?