'use strict'

const Main = (input) => {
  const X = parseInt(input.trim())

  let resultArr = []

  for (let i = 1; i <= X; i++) {
    const sqrt = Math.sqrt(i)
    if ((sqrt - Math.floor(sqrt)) === 0) {
      resultArr.push(i)
    }
  }

  let result = Math.max.apply(null, resultArr)

  console.log(result)
  return result
}

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