Sierra Mountain Escape

You and your friend is very fond of climbing. Nothing can compare with the rise in the impregnable mountain, setting a flag there, and then the descent from it. Your friend once went to the mountain Sierra, which you were going to climb together. He stuck to it and managed to convey a distress signal down. You need to help a friend to come down to this dangerous mountain, because soon there will be a storm, which will complicate the descent.