Untitled

// 2 
#include <iostream>
using namespace std;
int main()
{
    int a;
    cin >> a;
    int f = 0;
    while (a != 0)
    {
        if ((a % 10) % 2 == 0)
        {
            f += 1;
            a /= 10;
        }
        if ((a % 10) % 2 != 0)
        {
            a /= 10;
        }
        
    }
    cout << f;
    return 0;
}