Can you replace the question mark with a number?

An old lady, who lived on the third floor of a boardinghouse, broke her leg.
As the doctor put a cast on it, he warned her not to climb any stairs.
Several weeks later, the doctor took off the cast.
"Can I climb stairs now?" asked the little old lady.
"Yes," the doctor replied.
"Thank goodness!" she said. "I'm sick and tired of shimmying up and down that drainpipe!"