MATH PUZZLE: Can you replace...

A man was walking along the street when he saw a ladder going into the clouds. As any of us would do, he climbed the ladder. He reached a cloud, upon which sat a rather plump and very ugly woman. "Screw me or climb the ladder to success," she said.
No contest, thought the man, so he climbed the ladder to the next cloud. On this cloud was a slightly thinner woman, who was slightly easier on the eye. "Screw me hard or climb the ladder to success," she said. "Well," thought the man, "might as well carry on."
On the next cloud was an even more attractive lady who, this time, was quite attractive. "Screw me now or climb the ladder to success," she uttered. As he turned her down and went on up the ladder, the man thought to himself that this was getting better the further he went.
On the next cloud was an absolute beauty. Slim, attractive, the lot. "Screw me here and now or climb the ladder to success," she flirted. Unable to imagine what could be waiting, and being a gambling man, he decided to climb again. When he reached the next cloud, there was a 400 pound ugly man, arm pit hair showing, flies buzzing around his head.
"Who are you?" the man asked.
"Hello" said the ugly fat man, "I'm Cess!"