е - #5

public static String format(double input) {
    int ending = ((int) input);

    if ((ending % 100 >= 11) && (ending % 100 <= 20)) {
        return "рублей";
    }

    switch (ending % 10) {
        case 1: {
            return "рубль";
        }
        case 2:
        case 3:
        case 4: {
            return "рубля";
        }
        default: {
            return "рублей";
        }
    }
}