Amaterasu doesn't burn things instantly,
so before it could even burn a single hand,
the Buddha will most likely pulverize Madara or Sasuke
Part of the Buddha would be burning ofcourse thus the one that used Amaterasu would be trolled by now having a buddha + Amaterasu coming at him.
The Budha Would Be Like:
What is this Dog Piss On Me? i should Smack this Dog
Nice triple post m8.Buddha would die probably laughing