#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 base = 10001;
	//long long int max = strtoull( szRead, 0, 0 );
	long long int max = strtoul( szRead, 0, 0 );
	
	if( max < base )
	{
		printf( "0\n" );
		return 0 ;
	}

	int i = max / base;
	char temp[16] = "";
	sprintf( temp, "%d", i );
	int keta = strlen( temp );
	int count = 0;

	count += (keta-1) *9;

	char temp2[16] = "";
	for( int j = 0; j < keta; j++ )
	{
		temp2[j] = temp[0];
	}
	int k = atoi( temp2 );

	memset( temp2+1, 0,sizeof( temp2 )-1 );

	count += atoi( temp2 );
	if( i < k )
		count--;

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


	
	return 0;

}