“…Since impulsive problems are important in real world, many researchers have extensively studied the theory and applications of impulsive differential equations, see [2,4,5,8,11] for more details. In recent years, variational methods have been widely used to study Hamiltonian system and impulsive problems, see [1,3,6,7,9,[12][13][14][15][16][17] and references therein. In [7], Kyritsi and Papageorgion investigated problem (1.2) and obtained an existence result by using Morse critical groups.…”