function search(num) {
  const sqrt = Math.sqrt(num);
  if (Number.isInteger(sqrt)) {
    return num;
  } else {
    return search(num - 1);
  }
}

function main(input) {
  const result = search(Number(input))
  console.log(result);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'))
