public class AverageCalculator {
    public static void main(String[] args) {
        int a = 1000000000;
        int b = 2000000000;

        int avg = a/2 + b/2 + (a%2 + b%2)/2;

        System.out.println("avg = " + avg);
    }
}


//Тесты:
// a = 1, b = 2 , avg = 1
// a = 5, b = 9, avg = 7
// a = 1000000000, b = 2000000000, avg = 1500000000