12⁢π⁢∫-∞∞Γ⁡a+ⅈ⁢t⁢Γ⁡b+ⅈ⁢t⁢Γ⁡c-ⅈ⁢t⁢Γ⁡d-ⅈ⁢t⁢ⅆ⁡t=Γ⁡a+c⁢Γ⁡a+d⁢Γ⁡b+c⁢Γ⁡b+dΓ⁡a+b+c+d,