头条第一道笔试题，珠子的那个

求大神指教哪里出错了
if __name__=="__main__":
    try:
        n,m,c=map(int,raw_input().split())
        result=[]
        for i in range(1,n+1):
            result.append(map(int,raw_input().split()))
        l=[]   
        for j in range(len(result)-1):
            if len(result[j])==1:
                continue
            else:
                for k in result[j][1::]:
                    if k in result[j+1][1::]:
                        l.append(k)
        for k in result[n-1][1::]:
            if k in result[0][1::]:
                l.append(k)
        print l        
        print len(set(l))
    except:
        pass