I was trying to show whether or not the function:
$f: [0,1 ] \rightarrow \mathbb{R}$
$f(x)= \frac {1}{n}$ for $x = \frac {1}{n}$ $(n \in \mathbb{N})$
and
$f(x) = 1$ if the condition isn't satisfied
was integrable, but I'm having trouble figuring out the upper and lower sums. If anyone could point me in the right direction I would appreciate it.