\int _{C_R}\!{f(z)}{dz} + \int _{C_r}\!{f(z)}{dz} + \int _{2-r}^{\varepsilon}\!{f(z)}{dz} + \int _{C_{\varepsilon}}\!{f(z)}{dz} + \int _{\varepsilon}^{2-r}\!{f(z)}{dz} = 2 \pi i $Res$(f;-3)