struct Account {
    let currencyCode: String
    let openDate: Date
}

let currencyCodes = ["RUR": 0, "USD": 1, "EUR": 2]

func sortedAccounts(_ accounts: [Account]) -> [Account] {
    return accounts
        .sorted { first, second in

            switch first.currencyCode == second.currencyCode {
            case true:
                return first.openDate < second.openDate
            case false:
                let secondCurrency = currencyCodes[second.currencyCode] ?? Int.min
                let firstCurrency = currencyCodes[ first.currencyCode] ?? Int.max
                return firstCurrency < secondCurrency
            }
        }
}