Then area $A = \sqrt{s(s - a+1)(s - a)(s - a-1)} = \sqrt{ \frac{3a}{2} \cdot \left(\frac{3a}{2} - a + 1\right) \cdot \left(\frac{3a}{2} - a\right) \cdot \left(\frac{3a}{2} - a - 1\right)} $