def calculate_total_cost():
    try:
        x_qty, x_price = map(int, input().split())
        y_qty, y_price = map(int, input().split())
        z_qty, z_price = map(int, input().split())
        if x_qty < 0 or x_price < 0 or y_qty < 0 or y_price < 0 or z_qty < 0 or z_price < 0:
            print("Invalid input.")
            return
        total = (x_qty * x_price) + (y_qty * y_price) + (z_qty * z_price)
        print(total)
    except ValueError:
        print("Invalid input.")