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First repeated ticket

A scanner records ticket IDs in arrival order. Print the ID at the first repeated scan, or NONE when all IDs are unique. This is not the smallest repeated ID: the second appearance that occurs earliest wins. Ticket IDs are case-sensitive.

Input

One line of space-separated ticket IDs.

Output

One ID or NONE.

Example 1

Input

b a a b

Output

a

The second a appears before the second b, so a is the first repeated scan even though b appeared first.

Constraints

  • The scan line contains 1 to 200 IDs.
  • Ticket IDs are case-sensitive non-empty tokens.

Hints

Hint 1 of 2

A Set supports fast membership checks.

Hint 2 of 2

Walk input order and stop immediately when a repeated ID appears.

Solution

Show a reference solution and explanation
 JavaScript · reference solution
const seen = new Set();
let answer = 'NONE';
for (const id of readline().split(' ')) {
  if (seen.has(id)) { answer = id; break; }
  seen.add(id);
}
console.log(answer);

Why it works

The first time an ID enters the Set is not a duplicate; the next occurrence is. Returning at the first duplicate event preserves arrival order, unlike sorting or counting all IDs before choosing an answer.

Lesson for this exercise: JavaScript Arrays: Creating, Indexing and Changing Lists

Your program
const seen = new Set();
let answer = 'NONE';
for (const id of readline().split(' ')) {
  // Stop at the first ID already in seen.
}
console.log(answer);

Tests: 3 cases including the examples. Passing every test marks the exercise solved in this browser.

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