#include <iostream>
using namespace std;


int rec(int x) {
    if(x == 0) {
        return 0;
    }
    int cifra = x % 10;

    if(cifra % 2 == 0) {
        return rec(x / 10) + 1;
    }
    else {
        return rec(x / 10) + 0;
    }
}
int main() {
    int r = rec(1234);
    cout << r << endl;
    return 0;
}
// rec(1234) = rec(123) + 1 = 1 + 1 = 2
// rec(123) = rec(12) = 1
// rec(12) = rec(1) + 1 = 0 + 1 = 1
// rec(1) = rec(0) = 0
// rec(0) = 0