From The Tao of Programming...

A manager went to the master programmer and showed him the requirements
document for a new application. The manager asked the master: "How long will
it take to design this system if I assign five programmers to it?"
"It will take one year," said the master promptly.
"But we need this system immediately or even sooner! How long will it
take it I assign ten programmers to it?"
The master programmer frowned. "In that case, it will take two years."
"And what if I assign a hundred programmers to it?"
The master programmer shrugged. "Then the design will never be
completed," he said.
-- Geoffrey James, "The Tao of Programming"