Take 2 strings `s1` and `s2` including only letters from `a`to `z`.
Return a new **sorted** string, the longest possible, containing distinct letters,
- each taken only once - coming from s1 or s2.

# Examples:
```
a = "xyaabbbccccdefww"
b = "xxxxyyyyabklmopq"
longest(a, b) -> "abcdefklmopqwxy"

a = "abcdefghijklmnopqrstuvwxyz"
longest(a, a) -> "abcdefghijklmnopqrstuvwxyz"
```

Difficulty: EASY
Starter code: def longest(s1, s2):
	

Solutions:
def longest(a1, a2):
	return ''.join(sorted(set(a1 + a2)))


def longest(s1, s2):
	return ''.join(sorted(set(s1 + s2)))


def longest(s1, s2):
	alphabet = 'abcdefghijklmnopqrstuvwxyz'
	s = s1 + s2
	y = ''
	for x in alphabet:
		if x not in s:
			continue
		if x in s:
			y = y + x
	return y


def longest(s1, s2):
	distinct = set(s1 + s2)
	distinctSorted = sorted(distinct)
	return ''.join(distinctSorted)


def longest(s1, s2):
	x = ''
	y = sorted(s1 + s2)
	for i in y:
		if i not in x:
			x += i
	return x


def longest(s1, s2):
	set1 = set(s1)
	set2 = set(s2)
	return ''.join(sorted(set1 | set2))


import itertools

def longest(s1, s2):
	longest = ''
	for i in s1:
		if i not in longest:
			longest += i
	for i in s2:
		if i not in longest:
			longest += i
	return ''.join(sorted(longest))


def longest(s1, s2):
	freq = {}
	for c in list(s1):
		freq[c] = freq.get(c, 0) + 1
	for c in list(s2):
		freq[c] = freq.get(c, 0) + 1
	l = sorted([c for c in list(freq.keys())])
	return ''.join(l)


def longest(s1, s2):
	letters_count = [0] * 26
	for letter in s1:
		letters_count[ord(letter) - 97] += 1
	for letter in s2:
		letters_count[ord(letter) - 97] += 1
	result = []
	for i in range(26):
		if letters_count[i] > 0:
			result.append(chr(i + 97))
	return ''.join(result)


def longest(s1, s2):
	results = []
	for records in s1:
		if records not in results:
			results.append(records)
	for records in s2:
		if records not in results:
			results.append(records)
	results = sorted(results)
	return ''.join(results)


def longest(s1, s2):
	return ''.join(sorted(list(dict.fromkeys(s1 + s2))))


def longest(s1, s2):
	return ''.join([x for x in 'abcdefghijklmnopqrstuvwxyz' if x in s1 + s2])


longest = lambda x, y: ''.join(sorted(set(x + y)))


def longest(s1, s2):
	new_string = set(s1 + s2)
	sort_string = sorted(new_string)
	return ''.join((s for s in sort_string))


import string

def longest(s1, s2):
	comb = []
	alphabet = {}
	ind = 0
	for letter in s1:
		if letter in comb:
			pass
		else:
			comb.append(letter)
	for letters in s2:
		if letters in comb:
			pass
		else:
			comb.append(letters)
	lowerCase = list(string.ascii_lowercase)
	for letters in lowerCase:
		ind += 1
		alphabet[letters] = ind
	for x in range(len(comb)):
		for i in range(len(comb) - 1):
			if alphabet[comb[i]] > alphabet[comb[i + 1]]:
				(comb[i], comb[i + 1]) = (comb[i + 1], comb[i])
	comb = ''.join(comb)
	return comb


def longest(s1, s2):
	insieme = set()
	for char in s1 + s2:
		insieme.add(char)
	return ''.join(sorted(insieme))


def longest(s1, s2):
	result = ''
	for i in sorted(set(list(set(s1)) + list(set(s2)))):
		result += i
	return result


def longest(s1, s2):
	new_str = ''.join([s1, s2])
	s = list(new_str)
	s = list(set(s))
	s.sort()
	result = ''.join(s)
	return result