#include <iostream>
#include <vector>
using namespace std;

int rec(int number) {
    if(number == 0) {
        return 0;
    }
    int cifra = number % 10;
    return rec(number / 10) + cifra;
}
int main() {
    cout << rec(1234) << endl;

    return 0;
}


// rec(1234) = rec(123) + 4 = 6 + 4 = 10
// rec(123) = rec(12) + 3 = 3 + 3 = 6
// rec(12) = rec(1) + 2 = 1 + 2 = 3
// rec(1) = rec(0) + 1 = 0 + 1 = 1
// rec(0) = 0