At the faculty of mathematics, Orhan was faced with the following problem: find the number of positive integers from $1$ to $10^n$, which all digits are different. Since Orkhan also goes to computer science classes at FizMat Lyceum, he easily wrote a program that calculates the answer. And can you do it? \InputFile One integer $n~(1 \le n \le 18)$. \OutputFile Print the number of required positive integers.