3. Футы в дюймы и наоборот

#include <iostream>
int main() {
    char x, a; double f, i, r;
    std::cout << "If you want to conversion of foots in inches then write f" << "\n" << "If you want to conversion of inches in foots then write i" << std::endl;
    do {
        while (true) {
            std::cout << "What operation do you want to do ? " << std::endl;
            std::cin >> x;
            if (x == 'i' || x == 'f') { break; }
            else {
                std::cout << "You didn't enter operation. Try again." << std::endl;
                continue;
            }
        }
        if (x == 'f') {
            std::cout << "How many foots?" << std::endl;
            std::cin >> f;
            r = f * 12;
            std::cout << "In " << f << " foots " << r << " iches" << std::endl;
        }
        else if (x == 'i') {
            std::cout << "How many iches?" << std::endl;
            std::cin >> i;
            r = i / 12;
            std::cout << "In " << i << " iches " << r << " foots" << std::endl;
        }
        while (true) {
            std::cout << "Continue? (y or n)" << std::endl;
            std::cin >> a;
            if (a == 'y' || a == 'n') {break;}
            else {
                std::cout << "You didn't answer. Try again." << std::endl;
                continue;
            }
        }
    } while (a == 'y' || a!='n');
    return 0;
}