题解 | #玛雅人的密码##python3#

import sys
def swap(s,i,j):
    #print(i,j)
    if(j+1<len(s)):
        s=s[:i]+s[j]+s[i]+s[j+1:]
    elif(j+1==len(s)):s=s[:i]+s[j]
    else:s=s[:i]
    return s
def bfs(s,book):
    queue=[]
    queue.append([s,0])
    book.append(s)
    while(len(queue)):
        now=queue[0]
        queue=queue[1:]
        now_s=now[0]
        if(now_s.find('2012')!=-1):
            print(now[1])
            return 
        for i in range(len(now_s)):
            now_s=swap(now_s,i,i+1)
            if(now_s not in book):
                queue.append([now_s,now[1]+1])
                book.append(now_s)
            now_s=swap(now_s,i,i+1)
    print(-1)
for line in sys.stdin:
    a = int(line)
    string=input()
    bfs(string,[])