  Symbol-pair codes are proposed to guard against pair-errors in symbol-pair
read channels. The minimum symbol-pair distance plays a vital role in
determining the error-correcting capability and the constructions of
symbol-pair codes with largest possible minimum symbol-pair distance is of
great importance. Maximum distance separable (\,MDS\,) symbol-pair codes are
optimal in the sense that such codes can acheive the Singleton bound. In this
paper, for length $5p$, two new classes of MDS symbol-pair codes with minimum
symbol-pair distance seven or eight are constructed by utilizing repeated-root
cyclic codes over $\mathbb{F}_{p}$, where $p$ is a prime. In addition, we
derive a class of MDS symbol-pair codes with minimum symbol-pair distance seven
and length $4p$.
