#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define READ_BUFSIZE ( 128 )
#define READ_DELIMITER ( " " )


//標準入力取得（１行）

int GetStdin( char* pszStr, int lMaxLen )
{
	int lLen = 0;

    memset( pszStr, 0, lMaxLen );
    if( fgets( pszStr, lMaxLen, stdin ) )
    {
	    lLen = strlen( pszStr );
	    if( lLen >= 1 )
	    {
			if( pszStr[ lLen - 1 ] == 0x0A )
			{
				pszStr[ lLen - 1 ] = 0;
				lLen--;
			}
		}
	}
	
	return( lLen );
}


int main(int argc, char *argv[]) 
{
	char szRead[READ_BUFSIZE] = "";
	//char* psOutbuf[10000] = { 0 };
	int lInput[4] = {0};

	GetStdin( szRead, READ_BUFSIZE );

	long long int base = 1000000001;
	long long int max = strtoull( szRead, 0, 0 );
	//long long int max = strtoul( szRead, 0, 0 );
	
	long long int x = 0;
	char a[READ_BUFSIZE] = "";

	int count = 0;

	for( int i = 1;  base*i <= max; i++ )
	{
		sprintf( a, "%lld", base*i );
		int len = strlen( a );

		int j = 0;
		for( ; j < len / 2; j++ )
		{
			if( a[j] != a[len-j-1] )
				break;

		}
		
		if( j == len / 2 )
			count++;
	}

	printf( "%d\n", count );


	
	return 0;

}