function Main (N) {
  N = parseInt(N.split("\n")[0], 10);
  var i = N;
  while (true) {
    if (Math.sqrt(N, 2)%1 == 0) {
      console.log(N);
      break;
    }
    N--;
  }
}

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