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')