+50 \left(\frac{1}{2}+\frac{2}{3}+\frac{3}{4}+\frac{4}{5}\right)^2+\left(\frac{1}{2}+\frac{2}{3}+\frac{3}{4}+\frac{4}{5}\right)\cdot \frac{1}{2}-\left(1+\frac{1}{2}+\frac{2}{3}+\frac{3}{4}+\frac{4}{5}\right)\cdot \left(\frac{2}{3}+\frac{3}{4}+\frac{4}{5}\right)
