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// big int
const BigInt = function BigInt(n = '0') {
  const str = (n.join && n.join`` || n + '').replace(/^0+/, '') || '0';
  const sign = str[0] === '-' && +n !== 0;
  const arr = [...str.replace(/^\-/, '')].map(n => +n);
  
  const calcDbl = bi => {
    return [1, 2, 3].reduce(([dbl, acc]) => {
      acc = acc.add(acc);

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// array intersection that correctly handles also duplicates

const intersection = (a1, a2) => {
  const cnt = new Map();
  a2.map(el => cnt.set(el, cnt.has(el) ? cnt.get(el) + 1 : 1));
  return a1.filter(el => cnt.has(el)).filter(el => {
    const left = cnt.get(el);
    if (0 < left) {
      cnt.set(el, left - 1);
      return true;

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function groupBy(arr, fn) {
  fn = fn || ((o) => o);
  let g = [];
  let v = [];
  for (let i = 0; i < arr.length; ++i) {
    let val = fn(arr[i]);
    let idx = g.indexOf(val);
    if (idx === -1) {
      g.push(val);

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const findIndexes = (arr, fn) => {
  const res = [];
  arr.map((el, i, arr) => {
    if (fn(el, i, arr)) res.push(i);
  });
  return res;
};

// set prototype

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// code that generates BF (hardcoded) solution using js
// https://www.codewars.com/kata/bf-n-th-fibonacci-number/train/bf

const MAX = 100;
const flag = '+>';
const inp = ',';

const nestedLoop = n => {
  if (n > MAX) return '';
  return `-[

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const fib = n => {
  const sq5 = Math.sqrt(5);
  return (sq5 * (1+sq5)**n - sq5 * (1-sq5)**n) * 2**-n * 0.2;
};

const fib2n = f => {
  const sq5 = Math.sqrt(5);
  const phi = (1 + sq5) / 2;
  return Math.floor(Math.log(f * sq5 + 0.5) / Math.log(phi));
};

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const bijectiveBinary = {
  convertToInt: s => parseInt('1'+s.replace(/./g,d=>(+d)-1), 2) - 1,
  convertFromInt: i => (i+1).toString(2).substr(1).replace(/./g,d=>(+d)+1)
};

// codewars:
// https://www.codewars.com/kata/58f5e53e663082f9aa000060/solutions/javascript

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const Sieve = (max = 1e5) => {
  const maxi = Math.sqrt(max);
  const notPrime = new Int8Array(max);
  notPrime[0] = notPrime[1] = 1;
  for (let i = 2; i < maxi; ++i) {
    if (notPrime[i] === 0) {
      for (let j = 2*i; j < max; j += i) {
        notPrime[j] = 1;
      }
    }

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// input: array of bits
// [1,0,1,0,1,1]

function convertBit(p, v, i) {
  return p[i] = i && p[i-1] ? 1 - v : v, p;
}

function bin2gray(bits) {
  return bits.reduceRight(convertBit, bits);
}

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const convertToRoman = num => {
  const roman = [...'IVXLCDM'];
  const patt = [
    [],
    [0],
    [0, 0],
    [0, 0, 0],
    [0, 1],
    [1],
    [1, 0],