using System;

​

class Program {

    static void Main(string[] args) {

       int[,] B = new int[3, 4];

int sum = 0;

​

for (int i = 0; i < 3; i++) {

    for (int j = 0; j < 4; j++) {

        Console.Write("Enter value for B{i},{j}: " ,i ,j);

        B[i, j] = int.Parse(Console.ReadLine());

    }

}

​

for (int i = 0; i < 3; i++) {

    for (int j = 0; j < 4; j++) {

        sum += B[i, j];

    }

}

​

Console.WriteLine("The sum of all elements in the array is: {sum}");

​

    }

}

​