14⁢π⁢∫-∞∞∏k=14Γ⁡ak+ⅈ⁢t⁢Γ⁡ak-ⅈ⁢tΓ⁡2⁢ⅈ⁢t⁢Γ⁡-2⁢ⅈ⁢t⁢ⅆ⁡t=∏1≤j<k≤4Γ⁡aj+akΓ⁡a1+a2+a3+a4,