n = int(input())
s = n // 10 % 10
g = n // 1 % 10
b = g * 10 + s
if b > n:
    print(b)
else:
    print(n)
/**************************************************************
	Problem: 1625
	User: admin
	Language: Python
	Result: Accepted
	Time:104 ms
	Memory:34244 kb
****************************************************************/