--- /dev/null
+#!/usr/bin/python3
+
+import regex
+
+total_lines=0
+valid_lines=0
+for line in open("input.txt", "r"):
+ total_lines += 1
+ (min_count, max_count, letter, password) = regex.match('([0-9]+)-([0-9]+) ([a-z]): ([a-z]*)', line).group(1,2,3,4)
+ min_count=int(min_count)
+ max_count=int(max_count)
+ count = 0
+ for x in password:
+ if x == letter:
+ count += 1
+ if count >= min_count and count <= max_count:
+ valid_lines += 1
+
+print(valid_lines, "valid lines of", total_lines)