import std.stdio, std.conv, std.string, std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
void main(string[] args){ if(args.length > 1) if(args[1] == "-debug") DEBUG = 1; solve(); }
void log()(){ writeln(""); } void log(T, A ...)(T t, lazy A a){ if(DEBUG) write(t, " "), log(a); } bool DEBUG = 0; 
string read(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }
T read(T)(){ return read.to!T; }
T[] read(T)(long n){ return n.iota.map!(_ => read!T).array; }
T[][] read(T)(long m, long n){ return m.iota.map!(_ => read!T(n)).array; }
// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- //

void solve(){
	
	long n = read.to!long;
	
	bool[long] set;
	int ans;
	while(n > 0 && n !in set){
		ans += 1;
		set[n] = 1;
		n += 1;
		while(n % 10 == 0 && n > 0) n /= 10;
	}
	
	ans.writeln;
	
}
