a='abbba'num=len(a)if num%2==0: begin=0 end=len(a)-1 if a[begin] == a[end]: print('yes') else: print('not')else: mid=num//2+1 a.replace('%s'%a[mid],'') begin = 0 end = len(a) - 1 if a[begin] == a[end]: print('yes') else: print('not')