x = input()if len(x) % 2 == 0: x,y = x[0:len(x)//2],x[:(len(x)//2)-1:-1]if len(x) % 2 == 1: x,y = x[0:len(x)//2],x[:(len(x)//2):-1]
if x == y: print('yes')else: print('no')