from typing import Counter
import string


def find_version_sep(s):
    """Given a pure version string, find the character (most often) 
       separating version components"""
    i = 0
    s_len = len(s)
    char_count = Counter()
    if s[i] in ['v', 'V', 'r', 'R']:
        i += 1
    if s[i] == '/':
        i += 1
    while i < s_len:
        while i < s_len and s[i] in string.digits:
            i += 1
        if i < s_len:
            char_count[s[i]] += 1
            i += 1
    if len(char_count) > 0:
        most_common = char_count.most_common(1)
        char = most_common[0][0]
        if char in '._':
            return char
    return '.'