#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
#include <cmath>
using namespace std;
int rec(int number) {
    if(number == 0) {
        return 0;
    }
    return rec(number / 10) + (number % 10);
}
int main() {
    cout << rec(9145) << endl;
    return 0;
}


// rec(9145) = rec(914) + 5 = 14 + 5 = 19
// rec(914) = rec(91) + 4 = 10 + 4 = 14
// rec(91) = rec(9) + 1 = 9 + 1 = 10
// rec(9) = rec(0) + 9 = 0 + 9 = 9
// rec(0) = 0