#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define int long long
#define fs first
#define ss second
#define all(a) a.begin(), a.end()
#define print(a) \
for (auto x : a) \
cout << x << ' '; \
cout << endl;
#define printmp(a) \
for (auto x : a) \
cout << x.fs << ' ' << x.ss << endl;
void solve(){
int n, m;
cin >> n >> m;
vector<vector<char>> a(n, vector<char> (m));
for(int i = 0; i < n; i ++)
for(int j = 0; j < m; j ++)
cin >> a[i][j];
if(n <= 20 and m <= 20){
int ans = 0;
for(int i = 1; i <= n; i ++){
for(int j = 1; j <= m; j ++){
vector<vector<char>> b = a;
for(int i1 = 0; i1 <= n - i; i1 ++){
for(int i2 = 0; i2 <= m - j; i2 ++){
if(b[i1][i2] != '0'){
bool flag = 1;
for(int x = 0; x < i; x ++){
for(int y = 0; y < j; y ++){
if(b[i1 + x][i2 + y] == '0')
flag = false;
}
}
if(flag){
for(int x = 0; x < i; x ++){
for(int y = 0; y < j; y ++){
b[i1 + x][i2 + y] = '2';
}
}
}
}
}
}
int cnt = 0;
for(int i = 0; i < n; i ++){
for(int j = 0; j < m; j ++){
cnt += b[i][j] == '1';
}
}
if(cnt == 0)
ans = max(ans, i * j);
}
}
cout << ans;
return;
}
vector<vector<int>> dp_right(n, vector<int>(m)), dp_down(n, vector<int>(m));
for(int i = n - 1; i >= 0; i --){
for(int j = m - 1; j >= 0; j --){
if(a[i][j] == '1'){
dp_right[i][j] = (j == m - 1 ? 0 : dp_right[i][j + 1]) + 1;
dp_down[i][j] = (i == n - 1 ? 0 : dp_down[i + 1][j]) + 1;
}
else{
dp_right[i][j] = 0;
dp_down[i][j] = 0;
}
}
}
int x = m, y = n;
for(int i = 0; i < n; i ++){
for(int j = 0; j < m; j ++){
if(a[i][j] == '1'){
if(j == 0 or a[i][j - 1] == '0')
x = min(x, dp_right[i][j]);
if(i == 0 or a[i - 1][j] == '0')
y = min(y, dp_down[i][j]);
}
}
}
cout << x * y << endl;
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
// freopen("bomb.in", "r", stdin);
// freopen("bomb.out", "w", stdout);
int t = 1;
// cin >> t;
while(t --){
solve();
cout << endl;
}
}
