If $\left\{ a_{i} \right\}_{i = 1}^{n}$, where $n$ is an even\n integer, is an arithmetic progression with common difference 1 , and\n $\sum_{i = 1}^{n}\mspace{2mu} a_{i} = 192,\sum_{i = 1}^{n/2}\mspace{2mu} a_{2i} = 120$,\n and then $n$ is equal to