Complex Analysis: Properties of Contour Integrals

Demonstrate that $\int_{-\gamma} f(z)|dz|=\int_{\gamma} f(z)|dz|$ where $\gamma$ is a piecewise smooth path and $f$ is a function that is continuous on $|\gamma|$ .

This proof seems like it should be very simple, but I am not sure it is really saying that it's just turning a path around to go in the opposite direction. Could someone please help me out? Thanks.