#include <iostream>
using namespace std;

int apcif(int n, int c)
{//numarul de aparitii ale lui c in n
    if(n<=9) return n==c;
    else if(n%10==c) return apcif(n/10,c)+1;
         else return apcif(n/10,c);
}

int dist(int n, int c)
{//numara cifrele distincte ale lui n
    if(c==-1) return 0;
    else if(apcif(n,c)) return dist(n,c-1)+1;
         else return dist(n,c-1);
}

int main()
{
    int n;
    cin>>n;
    cout<<dist(n,9);
    return 0;
}

sau

#include <iostream>

using namespace std;

int apcif(int n, int c)
{//verific daca c apare in n
    if(n<=9) return n==c;
    else if(n%10==c) return 1;
         else return apcif(n/10,c);
}

int nrdist(int n)
{//numara cifrele distincte ale lui n
    if(n==0) return 0;
    else if(apcif(n/10,n%10)==0) return nrdist(n/10)+1;
         else return nrdist(n/10);
}

int main()
{
    int n;
    cin>>n;
    cout<<nrdist(n);
    return 0;
}