#include<bits/stdc++.h>
using namespace std;
#ifndef BADGNU
#pragma GCC target("sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#endif
#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ll long long
// #define int ll
#define ld long double
#define y1 cheza
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
template<class T> using ordered_set = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
template<class T> using ordered_multiset = tree<T,null_type,less_equal<T>,rb_tree_tag,tree_order_statistics_node_update>;
const int N=2600;
const int M=5001;
const int B=447;
const int mod=998244353;
const ll INF=1e18;
const int dx[]={1,-1,0,0};
const int dy[]={0,0,1,-1};
const double eps=1e-6;
int n,m;
char a[N][N];
int pref[N][N];
int calc(int x1,int y1,int x2,int y2){
return pref[x2][y2]-pref[x1-1][y2]-pref[x2][y1-1]+pref[x1-1][y1-1];
}
void test(){
cin>>n>>m;
for(int i=1;i<=n;i++){
for(int j=1;j<=m;j++){
cin>>a[i][j];
a[i][j]^=1;
pref[i][j]=pref[i-1][j]+pref[i][j-1]-pref[i-1][j-1]+a[i][j]-'0';
}
}
int x=2500;
int y=2500;
for(int i=1;i<=n;i++){
for(int j=1;j<=m;j++){
if(a[i][j]=='1')continue;
if(a[i][j-1]=='0'||a[i-1][j]=='0')continue;
int l=i;
int r=n;
while(l<=r){
int mid=(l+r)>>1ll;
if(calc(i,j,mid,j)==0){
l=mid+1;
}
else{
r=mid-1;
}
}
int x2=l-1;
l=j;
r=m;
while(l<=r){
int mid=(l+r)>>1ll;
if(calc(i,j,x2,mid)==0){
l=mid+1;
}
else{
r=mid-1;
}
}
int y2=l-1;
x=min(x,(x2-i+1));
y=min(y,(y2-j+1));
}
}
for(int i=1;i<=n;i++){
for(int j=1;j<=m;j++){
if(a[i][j]=='1')continue;
if(a[i][j-1]=='0'||a[i-1][j]=='0')continue;
int l=j;
int r=m;
while(l<=r){
int mid=(l+r)>>1ll;
if(calc(i,j,i,mid)==0){
l=mid+1;
}
else{
r=mid-1;
}
}
int y2=l-1;
l=i;
r=n;
while(l<=r){
int mid=(l+r)>>1ll;
if(calc(i,j,mid,y2)==0){
l=mid+1;
}
else{
r=mid-1;
}
}
int x2=l-1;
x=min(x,(x2-i+1));
y=min(y,(y2-j+1));
}
}
cout<<x*y<<'\n';
}
/*
*/
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// cout.tie(nullptr);
int t2=1;
// cin>>t2;
for(int i=1;i<=t2;i++){
test();
}
}
