The transformation occurring in the Duma's method is given below
\( \mathrm{C_2H_7N} + \left( 2x + \frac{y}{2} \right)\mathrm{CuO} \rightarrow x\mathrm{CO_2} + \frac{y}{2}\mathrm{H_2O} + \frac{z}{2}\mathrm{N_2} + \left( 2x + \frac{y}{2} \right)\mathrm{Cu} \)
The value of \( y \) is _________ . (Integer answer)