3.6

#include <iostream>

using namespace std;

long a;

void input() {
    cout << "Enter a: ";
    cin >> a;
}

int countZeroes(long num) {
    int count = 0;
    while (num != 0) {
        if (num % 10 == 0) {
            count++;
        }
        num /= 10;
    }
    return count;
}

int main() {

    input();

    cout << "Result: " << countZeroes(a) << endl;

}