Boundary Values & Fourier Series · Easy problem

Let $f(x) = 0$ for $-1 < x < 0$ and $f(x) = 1$ for $0 < x < 1$. In its Fourier series on $[-1, 1]$, $b_n = \displaystyle\int_{-1}^{1} f(x)\sin(n\pi x)\,dx$. Find $b_1$.