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  scu09156146  commented on April 26, 2024, 2:00 p.m.

  題解

  import java.util.Scanner;
  
  public class TriangleArea {
  
      public static void main(String[] args) {
          Scanner input = new Scanner(System.in);
          int n = input.nextInt();
          input.close();
          // 呼叫副程式，印出回傳值(四捨五入，小數點後兩位)
          System.out.printf("%.2f", area(n));
      }
  
      public static double area(int n) {
          return Math.sqrt(3) / 4 * n * n; // 正三角形面積公式
      }
  
  }