import java.io.*;
class calc
{
	public static void main (String [] args) throws Exception
	{
		// INPUT
		// 3 Strings
			// 1 for commands
			// 2 for numbers
		// Buffered Reader
		
		// COMPUTATION
		// 3 doubles
			// 1 for answer
			// 2 for input #s
			
		// WHILE (boolean endprog)
			// get input
			// do calculations
			// ouput results
			// get input for repeating loop
			
		// VARIABLES
		String command = "";
		String in1 = "";
		String in2 = "";
		String repeat="yes";
		BufferedReader br = new BufferedReader (new InputStreamReader(System.in));
		
		double ans=0;
		double num1=0;
		double num2=0;
		
		boolean doAgain = true;
		
		while (doAgain)
		{
			
			// Get input
			System.out.print("Enter a number: ");
			in1=br.readLine();
			
			System.out.print("Enter a number: ");
			in2=br.readLine();
			
			boolean valid=true;
			
			System.out.println("Choose a operation: (a)dd, (s)ubtract, (m)ultiply, (d)ivide");
			command=br.readLine();
				
			// Change Strings to Doubles
			num1=Double.parseDouble(in1);
			num2=Double.parseDouble(in2);
			
			//System.out.println("num1: "+num1+" num2: "+num2);
			//doAgain=false;
			
			if (command.equals("a"))
			{
				ans=num1+num2;	
			}
				
			else if (command.equals("s"))
			{
				ans=num1-num2;	
			}
			else if (command.equals("m"))
			{
				ans=num1*num2;	
			}
			else if (command.equals("d"))
			{
				ans=num1/num2;	
			}
			else
				System.out.println("ERROR 1: Invalid operator");
			
			System.out.println("The answer is: "+ans);
			
			System.out.print("Do another calculation yes/no ?");
			repeat=br.readLine();
			if (repeat.equals("yes"))
				doAgain=true;
			else
				doAgain=false;
		}
	}	
}