AtCoder Beginner Contest 002 D – 派閥

import itertools
 
n , m = map(int,input().split())
r = []
 
for i in range(m):
    r.append(set(map(int,input().split())))
 
chmax = 1
 
for i in range(2 ** n):
    h = []
    for j in range(n):
        if (i >> j) & 1:
            h.append(j + 1)
    
    C=itertools.combinations(h,2)
    ok = True
    for c in C:
        if set(c) not in r:
            ok = False
            break
    if ok:
        chmax = max(chmax,len(h))
        
print(chmax)