Problem:
Score : 200 points

Problem Statement

Find the largest square number not exceeding N. Here, a square number is an integer that can be represented as the square of an integer.

Constraints

1 \leq N \leq 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the largest square number not exceeding N.

Sample Input 1

10

Sample Output 1

9

10 is not square, but 9 = 3 × 3 is. Thus, we print 9.

Sample Input 2

81

Sample Output 2

81

Sample Input 3

271828182

Sample Output 3

271821169

Solution in JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

function Main(input){
  var num = parseInt(input);

  // 与えられる数から順に１ずつ引いていき、平方根が整数になる値を求める
  for(var i = num; i > 1; i--){ 
    if(Math.sqrt(i) % 1 === 0){
      console.log(i);
      break;
    }
  }
}

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