function currencyConverter([arg1, arg2, arg3]) {
    let quantity = Number(arg1);
    let sourceCurrency = arg2.toLowerCase();
    let convertedCurrency = arg3.toLowerCase();

    if (sourceCurrency == 'bgn') {
        quantity = quantity / 1;
    } else if (sourceCurrency == 'usd') {
        quantity = quantity / 1.79549;
    } else if (sourceCurrency == 'gbp') {
        quantity = quantity / 2.53405;
    } else if (sourceCurrency == 'eur') {
        quantity = quantity / 1.95583;
    }

    if (convertedCurrency == 'bgn') {
        quantity = quantity * 1;
    } else if (convertedCurrency == 'usd') {
        quantity = quantity * 1.79549;
    } else if (convertedCurrency == 'gbp') {
        quantity = quantity * 2.53405;
    } else if (convertedCurrency == 'eur') {
        quantity = quantity * 1.95583;
    }
    console.log(quantity.toFixed(2) + ' ' + convertedCurrency)
}
currencyConverter(['20', 'gbp', 'bgn'])