h,w=map(int,input().split())
X=[]
for i in range(h):
    A=list(map(int,input().split()))
    X.append(A)

def f(i,j):
    X[i][j]=1-X[i][j]
    X[i+1][j]=1-X[i+1][j]
    X[i][j+1]=1-X[i][j+1]
    X[i+1][j+1]=1-X[i+1][j+1]

for i in range(h-1):
    for j in range(w-1):
        if X[i][j]:
            f(i,j)
A=[]
B=[]
for i in range(h):
    A.append(X[i][-1])
for i in range(w):
    B.append(X[-1][i])
ans=sum(A)+sum(B)-A[-1]
if A[-1]+A[-2]+B[-2]==3:
    ans-=2
print(ans)
"""
C=[]
D=[]
pre=0
for i in A:
    if i:
        pre+=1
    else:
        C.append(pre)
        pre=0
C.append(pre)
pre=0
for i in B:
    if i:
        pre+=1
    else:
        D.append(pre)
        pre=0
D.append(pre)
print(C)
print(D)
c=0
for i in C:
    c+=i//2
d=0
for i in D:
    d+=i//2
print(ans-min(c,d)*2)
"""