const fibonacci = function (number) {
  if (number < 0) return "OOPS";
  if (number === 0) return 0;

  let prev1 = 1;
  let prev2 = 0;

  for (let i = 2; i <= number; i++) {
    let current = prev1 + prev2;
    prev2 = prev1;
    prev1 = current;
  }

  return prev1;
};

// Do not edit below this line
module.exports = fibonacci;