var accounts = {

a: 100,

b: 0,

c: 20

};

function getAccount() {

let accountName = prompt("Enter an account name");

if (!accounts.hasOwnProperty(accountName)) {

throw new Error(`No such account: ${accountName}`);

}

return accountName;

}

function transfer(from, amount) {

if (accounts[from] < amount) return;

accounts[from] -= amount;

accounts[getAccount()] += amount;

}

function transfer(from, amount) {

if (accounts[from] < amount) return;

let progress = 0;

try {

accounts[from] -= amount;

progress = 1;

accounts[getAccount()] += amount;

progress = 2;

} finally {

if (progress == 1) {

accounts[from] += amount;

}

}

}

var InputError = class InputError extends Error {}

function promptDirection(question) {

let result = prompt(question);

if (result.toLowerCase() == "left") return "L";

if (result.toLowerCase() == "right") return "R";

throw new InputError("Invalid direction: " + result);

}