/*
TASK: SUB
LANG: C++
*/

#include <iostream>
using namespace std;

int n;

int main () {
	scanf("%d",&n);
	int i=0,k=0,st;
	while (n>0) {
		k=0;
		st=n;
		while (st>0) {
			if (k<st%10) k=st%10;
			st/=10;
		}
		n-=k;
		i++;
	}
	printf("%d\n",i);
	return 0;
}
