//Nguyen Huu Hoang Minh
#include <bits/stdc++.h>
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define reset(x) memset(x, 0,sizeof(x))
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define N 2005
#define remain(x) if (x > MOD) x -= MOD
#define ii pair<int, int>
#define iiii pair< ii , ii >
#define viiii vector< iiii >
#define vi vector<int>
#define vii vector< ii >
#define bit(x, i) (((x) >> (i)) & 1)
#define Task "test"
#define int long long

using namespace std;

typedef long double ld;
const int inf = 1e10;
const int minf = -1e10;

int n, m;
int a[1005][1005];
int h[1005];
int pre[1005], nex[1005], x[1005], y[1005];

void readfile()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    if (fopen(Task".inp","r"))
    {
        freopen(Task".inp","r",stdin);
        //freopen(Task".out","w",stdout);
    }
    cin >> n >> m;
    for(int i=1; i<=n; i++){
        for(int j=1; j<=m; j++){
            cin >> a[i][j];
            //cout << a[i][j] << " \n"[j==m];
        }
    }
}

void proc()
{
    int ans = 1;
    for(int day=1; day <= n; day++){
        for(int i=1; i<=m; i++){
            if (day==1) h[i]=1;
            else{
                if (a[day][i]==a[day-1][i]) h[i] = 1;
                else h[i]++;
            }
        }
        h[0] = minf;
        stack<int> st;
        st.push(0);
        for(int i=1; i<=m; i++){
            while (st.size() && h[st.top()] >= h[i]) st.pop();
            pre[i] = st.top();
            st.push(i);
        }
        while (st.size()) st.pop();
        h[m+1] = minf;
        st.push(m+1);
        for(int i=m; i>=1; i--){
            while (st.size() && h[st.top()] >= h[i]) st.pop();
            nex[i] = st.top();
            st.push(i);
        }
        x[1] = 1;
        for(int i=2; i<=m; i++){
            x[i] = (a[day][i]!=a[day][i-1] ? x[i-1] : i);
        }
        y[m] = m;
        for(int i=m-1; i>=1; i--){
            y[i] = (a[day][i]!=a[day][i+1] ? y[i+1] : i);
        }
        int res=0;

        for(int i=1; i<=m; i++) ans = max(ans, h[i]*(min(y[i],nex[i]-1)-max(x[i],pre[i]+1)+1));
    }
    cout << ans;
}

signed main()
{
    readfile();
    proc();
    return 0;
}