using System;
using System.Data;

internal class Program
{
static void Main(string[] args)
{
const string CommandConvertRubToUsd = "1";
const string CommandConvertUsdToRub = "2";
const string CommandConvertRubToEur = "3";
const string CommandConvertEurToRub = "4";
const string CommandConvertEurToUsd = "5";
const string CommandConvertUsdToEur = "6";
const string CommandExit = "7";

float rubInWallet = 10000f;
float usdInWallet = 300f;
float eurInWallet = 0f;
bool isWork = true;

while (isWork)
{
Console.Clear();
Console.WriteLine($"На счете:\nРубли - {rubInWallet}\nДоллары - {usdInWallet}\nЕвро - {eurInWallet}");
Console.ReadKey();

Console.WriteLine($"{CommandConvertRubToUsd}" +
$"\n{CommandConvertUsdToRub}" +
$"\n{CommandConvertRubToEur}" +
$"\n{CommandConvertEurToRub}" +
$"\n{CommandConvertUsdToEur}" +
$"\n{CommandConvertEurToUsd}" +
$"\n{CommandExit} - Завершить программу.");

string userInput = Console.ReadLine();

switch (userInput)
{
case CommandConvertRubToUsd:

break;

case CommandConvertUsdToRub:

break;

case CommandConvertRubToEur:

break;

case CommandConvertEurToRub:

break;

case CommandConvertEurToUsd:
break;

case CommandConvertUsdToEur:
break;

case CommandExit:
isWork = false;
Console.WriteLine("Программа завершена.");
break;

default:
Console.WriteLine("Ошибка ввода!");
break;
}
}

Console.ReadKey();
}
}