#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 2.5e3 + 42, INF = 1e18 + 42;
bool alien[N*N];
vector<int> add[N*N];
int n, m, t[N*N], id[N][N], sz[N*N];
int F(int i) {
if(sz[i] < 0)
return i;
return sz[i] = F(sz[i]);
}
int getSz(int i) {
return -sz[F(i)];
}
void U(int a, int b) {
a = F(a), b = F(b);
if(a == b)
return;
if(-sz[a] < -sz[b])
swap(a, b);
sz[a] += sz[b];
sz[b] = a;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
for(int& p : sz)
p = -1;
cin >> n >> m;
n++, m++;
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++)
id[i][j] = m * i + j;
for(int i = 1; i < n; i++)
for(int j = 1; j < m; j++) {
char c; c = '1';//cin >> c;
alien[id[i][j]] = (c == '1');
}
int minLen = INF;
for(int i = 1; i < n; i++)
for(int j = 1; j < m; j++)
if(alien[id[i][j]]) {
t[id[i][j]] = t[id[i][j]-1] + 1;
add[t[id[i][j]]].push_back(id[i][j]);
if(j == m || !alien[id[i][j]+1])
minLen = min(minLen, t[id[i][j]]);
}
int ans = 0;
multiset<int> len;
for(int i = N*N-1; i > 0; i--) {
for(int j : add[i]) {
if(t[j - m] >= t[j]) {
len.erase(len.find(getSz(j - m)));
U(j - m, j);
}
if(t[j + m] > t[j]) {
len.erase(len.find(getSz(j + m)));
U(j + m, j);
}
len.insert(getSz(j));
}
if(i <= minLen) {
auto it = len.begin();
ans = max(ans, (*it) * i);
}
}
cout << ans;
}
