class and Control: Grade Calculator

In this problem, you will create a program that instantiates a GradeCalculator class, calls its methods to compute the average of three subject scores and determine a letter grade (A/B/C), and displays the full grade report to standard output.

Learning Objective: Control program flow with class instantiation and method calls

Create GradeCalculator class to calculate average from multiple subject scores and determine evaluation. Learn how to control program execution order by creating objects and calling methods.

Understanding with Concrete Examples

Example 1: High Score (A Grade)

Input:
90
85
88

Output:
Grade Report:
Math: 90points
English: 85points
Japanese: 88points
Average: 87points
Grade: A
```java

### Example 2: Medium Score (B Grade)
```java
Input:
70
65
68

Output:
Grade Report:
Math: 70points
English: 65points
Japanese: 68points
Average: 67points
Grade: B
```java

### Example 3: Boundary Value (Exactly 80)
```java
Input:
80
80
80

Output:
Grade Report:
Math: 80points
English: 80points
Japanese: 80points
Average: 80points
Grade: A
```java

## Input
Line 1: Math score (integer, 0-100)
Line 2: English score (integer, 0-100)
Line 3: Japanese score (integer, 0-100)

## Output
```java
Grade Report:
Math: [math]points
English: [english]points
Japanese: [japanese]points
Average: [average]points
Grade: [grade]
```java

Grade criteria:
- 80 or above: A
- 60 or above: B
- Below 60: C.