integration - How to show the following inequality in Measure Theory

How to show the following inequality in Measure Theory:

If $f$ is a non-negative measurable function defined on a measurable set $E$ then for any $\lambda >0$ we have $m\{x\in E:f(x)>\lambda \}\le\frac{1}{\lambda}\int _E f$ where $m$ denotes measure of a set

I can't figure out how to approach the above problem.Please give some hints.