const main = stdin => {
  const input = stdin.trim().split('\n')
  const [X] = input[0].split(' ').map(x => parseInt(x))

  for (let i = X; i >= 1; i--) {
    if (Math.sqrt(i) % 1 === 0) {
      console.log(i)
      break
    }
  }
}


// 標準入力
main(require("fs").readFileSync("/dev/stdin", "utf8"))
