成环WA

[王希元]

n,m=[int(i)for i in input().split()]
a=[['x']+[int(i)for i in input().split()]+['x']for k in range(n)]
a=[['x' for i in range(m+2)]]+a+[['x' for i in range(m+2)]]
def f(i,j,x,y):
    global a
    global i0
    global j0
   
    for [k,l] in [[i+1,j],[i,j+1],[i,j-1],[i-1,j]]:
       
        if a[k][l]==1 and (k!=x or l!=y)：
           
            if  [k,l]==[i0,j0] :
                print("YES")
               
                quit()
            else:
               
                f(k,l,i,j)

for i in range(1,n+1):
    for j in range(1,m+1):
        if a[i][j]==1:
            i0=i
            j0=j
            f(i,j,i,j)

print('No')