import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.lang.Math;
class AverageDemo {
    static float average(float a, float b){
	    return (a+b)/2;
    }

    public static void main(String[] args) throws java.io.IOException{
		    float a, b;
		    System.out.println("input two numbers");
	            BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
		    a = Float.parseFloat(input.readLine());
		    b = Float.parseFloat(input.readLine());
		    System.out.println("output:");
		    System.out.println(average(a, b));

                    
                    
                    

    }
}

//By msglm; Licensed under the AGPL v3