Nirvana

给出n，求1到n每个数字的每一位乘积的最大值

Kurt reaches nirvana when he finds the product of all the digits of some positive integer. Greater value of the product makes the nirvana deeper. Help Kurt find the maximum possible product of digits among all integers from $ 1 $ to $ n $ .

The only input line contains the integer $ n $ ( $ 1 \le n \le 2\cdot10^9 $ ).

Print the maximum product of digits among all integers from $ 1 $ to $ n $ .

390

216

7

7

1000000000

387420489

In the first example the maximum product is achieved for $ 389 $ (the product of digits is $ 3\cdot8\cdot9=216 $ ). In the second example the maximum product is achieved for $ 7 $ (the product of digits is $ 7 $ ). In the third example the maximum product is achieved for $ 999999999 $ (the product of digits is $ 9^9=387420489 $ ).