A8864 | Undoubtedly Lucky Numbers

Polycarpus loves lucky numbers. Everybody knows that lucky numbers are positive integers, whose decimal representation (without leading zeroes) contain only the lucky digits $x$ and $y$ . For example, if $x=4$ , and $y=7$ , then numbers 47, 744, 4 are lucky.

Let's call a positive integer $a$ undoubtedly lucky, if there are such digits $x$ and $y$ $(0<=x,y<=9)$ , that the decimal representation of number $a$ (without leading zeroes) contains only digits $x$ and $y$ .

Polycarpus has integer $n$ . He wants to know how many positive integers that do not exceed $n$ , are undoubtedly lucky. Help him, count this number.

The first line contains a single integer $n$ $(1<=n<=10^{9})$ — Polycarpus's number.

Print a single integer that says, how many positive integers that do not exceed $n$ are undoubtedly lucky.