Solution.java

import java.util.Scanner;

public class MissingNumber {
    public static int findMissingNumber(int[] arr, int n) {
        int total = (n + 1) * (n + 2) / 2; // Sum of 1 to n+1
        for (int num : arr) {
            total -= num; // Subtract array elements from total
        }
        return total;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter the size of the array (n): ");
        int n = scanner.nextInt();

        int[] arr = new int[n];
        System.out.print("Enter " + n + " elements of the array: ");
        for (int i = 0; i < n; i++) {
            arr[i] = scanner.nextInt();
        }

        int missingNumber = findMissingNumber(arr, n);
        System.out.println("The missing number is: " + missingNumber);
    }
}