function main(input) {
  var a = input[0]-0;
  var ans = 0;
  for(var i=0;i<=Math.sqrt(a);i++){
    if(i*i<=a) ans = i*i;
  }
  console.log(ans);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"))
