#include 
#include 
#include 
using namespace std;

int rec(int x) {
    if(x == 0) {
        return 0;
    }
    int cifra = x % 10;
    return rec(x / 10) + cifra;
}
int main() {
    cout << rec(3456) << endl;
    return 0;
}
// rec(3456) = rec(345) + 6 = 12 + 6 = 18
// rec(345)  = rec(34) + 5 = 7 + 5 = 12
// rec(34)   = rec(3) + 4 = 3 + 4 = 7
// rec(3)    = rec(0) + 3 = 0 + 3 = 3
// rec(0) = 0