#include <cassert>
#include <iostream>

extern "C" int guide_double_small(int value);

class Calculator {
public:
    static int double_small(int value) {
        return (value >= 0 && value <= 100) ? value * 2 : -1;
    }
};

extern "C" int guide_double_small(int value) {
    return Calculator::double_small(value);
}

int main() {
    assert(guide_double_small(4) == 8);
    assert(guide_double_small(101) == -1);
    std::cout << guide_double_small(4) << '\n';
}