#include <iostream>

int count_even_before(int n) {
    if (n < 0 || n > 100) {
        return -1;
    }
    int count{0};
    for (int i{0}; i < n; ++i) {
        if (i % 2 == 0) {
            count += 1;
        }
    }
    return count;
}

int main() {
    int first{count_even_before(0)};
    int second{count_even_before(1)};
    int third{count_even_before(5)};
    int again{count_even_before(5)};
    std::cout << first << '\n';
    std::cout << second << '\n';
    std::cout << third << '\n';
    std::cout << again << '\n';
    return 0;
}