Olá! Segue resolução da minha atividade:
a = int(input("Specify the days for the activities: "))
b = int(input("Specify the days for the activities: "))
c = int(input("Specify the days for the activities: "))
if a < 0 or b < 0 or c < 0:
print("Error: The days cannot be negative.")
else:
result = sum([a, b, c])
print(f"The end result is: {result}")