#include <bits/stdc++.h>

using namespace std;

int zero_matrix(vector<vector<int>> a) {
    int n = a.size();
    int m = a[0].size();
	for(int i=0; i<n; ++i) for(int j=0; j<m; ++j) a[i][j]=!a[i][j];

    int ans = 0;
    vector<int> d(m, -1), d1(m), d2(m);
    stack<int> st;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            if (a[i][j] == 1)
                d[j] = i;
        }

        for (int j = 0; j < m; ++j) {
            while (!st.empty() && d[st.top()] <= d[j])
                st.pop();
            d1[j] = st.empty() ? -1 : st.top();
            st.push(j);
        }
        while (!st.empty())
            st.pop();

        for (int j = m - 1; j >= 0; --j) {
            while (!st.empty() && d[st.top()] <= d[j])
                st.pop();
            d2[j] = st.empty() ? m : st.top();
            st.push(j);
        }
        while (!st.empty())
            st.pop();

        for (int j = 0; j < m; ++j)
            ans = max(ans, (i - d[j]) * (d2[j] - d1[j] - 1));
    }
    return ans;
}

int solve_row(vector<int> row) {
	int n = row.size();
	vector<array<int,2> > a(n);
	vector<int> l(n,-1);
	vector<int> r(n,-1);
	for(int i=0; i<n; ++i) a[i] = {row[i],i};
	sort(a.rbegin(),a.rend());
	int ans=0;
	for(auto [v,i]: a) {
		l[i]=r[i]=i;
		if(i&&l[i-1]!=-1) l[i]=l[i-1];
		if(i<n-1&&r[i+1]!=-1) r[i]=r[i+1];
		r[l[i]]=r[i];
		l[r[i]]=l[i];
		ans=max(ans, (r[i]-l[i]+1)*v);
	}
	return ans;
}

int solve(vector<vector<int> > a) {
	int n = a.size();
	int m = a[0].size();
	for(int i=n-2; i>=0; --i) {
		for(int j=0; j<m; ++j) {
			a[i][j] = a[i][j]?1+a[i+1][j]:0;
		}
	}
	int ans = 0;
	for(int i=0; i<n; ++i) {
		ans=max(ans,solve_row(a[i]));
	}
	return ans;
}

int solve_slow(vector<vector<int> > a) {
	int n = a.size(), m = a[0].size();
	vector<vector<int> > v(n+1,vector<int>(m+1,0));
	for(int i=n-1; i>=0; --i) for(int j=m-1; j>=0; --j) {
		v[i][j]=a[i][j]+v[i+1][j]+v[i][j+1]-v[i+1][j+1];
	}
	int ans=0;
	for(int i1=0; i1<n; ++i1) {
		for(int j1=0; j1<m; ++j1) {
			for(int i2=i1+1; i2<=n; ++i2) {
				for(int j2=j1+1; j2<=m; ++j2) {
					int s = v[i1][j1]-v[i2][j1]-v[i1][j2]+v[i2][j2];
					int a = (i2-i1)*(j2-j1);
					if(a==s) ans = max(ans,a);
				}
			}
		}
	}
	return ans;
}

signed main() {
	cin.tie(0);
	ios_base::sync_with_stdio(0);
	
	int n,m;
	cin>>n>>m;
	vector<vector<int> > a(n,vector<int>(m));
	for(int i=0; i<n; ++i) for(int j=0; j<m; ++j) cin>>a[i][j];
	for(int i=0; i<n; ++i) for(int j=0; j<m; ++j) {
		int bij;
		cin>>bij;
		a[i][j]=(a[i][j]==bij);
	}
	cout<<zero_matrix(a)<<endl;
	return 0;

	/*
	srand(4);
	int n=19,m=19;
	while(1) {
		vector<vector<int> > a(n,vector<int>(m));
		for(int i=0; i<n; ++i) for(int j=0; j<m; ++j) a[i][j]=rand()%4==0;
		if(solve(a)!=solve_slow(a)) {
			cerr<<"found"<<endl;
			return 0;
		}
	}
	return 0;
	*/
}