#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<cstdio>
#define ll long long
using namespace std;
inline int read()
{
    int x=0,f=1;char s=getchar();
    while(s<'0'||s>'9'){if(s=='-')f=-1;s=getchar();}
    while(s<='9'&&s>='0'){x=x*10+s-'0';s=getchar();}
    return x*f;
}
int main()
{
    char ch[50];
    scanf("%s",ch);
    bool flag=true;
    for(int i=1;i<strlen(ch);i++)
        if(ch[i]!='9')flag=false;
    if(flag)printf("%d\n",(strlen(ch)-1)*9+ch[0]-'0');else
        printf("%d\n",(strlen(ch)-1)*9+ch[0]-'0'-1);
    return 0;
}

