#!/usr/bin/env python3

def correct_sentence(text: str) -> str:
    text_list = [x for x in text]
    text_list[0] = text_list[0].upper()

    if text_list[-1:] != '.':
        text_list.append('.')

    return ''.join(text_list)

print(correct_sentence('greetings, friends'))    
print(correct_sentence('greetings, friends.'))