Example.

$a=\frac{\sum_{i=0}^n \left(\frac{2}{3}\right)^{i}(i+1)}{1 + \sum_{i=0}^n \left(\frac{2}{3}\right)^{i}(i+1)}$

int main() {
  int x, y;
  scanf("%d%d", &x, &y);
  printf("%d", x + y);
}