The common difference of the A.P.: a_1, a_2, …, a_m is 13 more than the common difference of the A.P.: b_1, b_2, …, b_n. If b_31=-277, b_43=-385 and…

The common difference of the A.P.: $\displaystyle a_1, a_2, \ldots, a_{\mathrm{m}}$ is $\displaystyle 13$ more than the common difference of the A.P.: $\displaystyle b_1, b_2, \ldots, b_n$. If $\displaystyle b_{31}=-277, b_{43}=-385$ and $\displaystyle a_{78}=327$, then $\displaystyle a_1$ is equal to