노트

n = int(input()) a,b = map(int,input().split()) m = int(input()) relation = [[0]*101 for _ in range(101)] visited = [0]*101 q = [] for i in range(m): x,y = map(int,input().split()) relation[x][y]=relation[y][x]=1 def dfs(): visited[a]=1 q.append(a) while q: k = q.pop(0) if k==b: return for j in range(1,n+1): if relation[k][j]==1 and visited[j]==0: visited[j]=visited[k]+1 q.append(j) dfs() if vis..