#pragma GCC optimize("O3")
#pragma GCC target("popcnt")
#include <bits/stdc++.h>
using namespace std;
#define IShowSpeed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define popcnt __builtin_popcount
#define all(a) a.begin(),a.end()
#define pii pair<int,int>
#define mii map<int,int>
#define pll pair<ll,ll>
#define mll map<ll,ll>
#define pb push_back
#define vt vector
#define endl '\n'
#define X first
#define Y second
typedef long double ld;
typedef long long ll;
const ll dx[4]={1,-1,0,0},dy[4]={0,0,1,-1},N=1e6+10;
const ll mod=1e9+7,inf=1e18;
void solve(){
int n,m;
cin>>n>>m;
char a[n+2][m+2],c[n+2][m+2];
for(int i=1; i<=n; ++i) for(int j=1; j<=m; ++j) cin>>a[i][j];
int ans=0;
for(int x=1; x<=n; ++x){
for(int y=1; y<=m; ++y){
for(int i=1; i<=n; ++i) for(int j=1; j<=m; ++j) c[i][j]=a[i][j];
for(int i=1; i<=n; ++i) for(int j=1; j<=m; ++j){
int bad=1;
for(int ol=i; ol<=i+x-1; ++ol) for(int zhas=j; zhas<=j+y-1; ++zhas) if(c[ol][zhas]=='0') bad=0;
if(bad) for(int ol=i; ol<=i+x-1; ++ol) for(int zhas=j; zhas<=j+y-1; ++zhas) c[ol][zhas]='2';
}
int ok=1;
for(int ol=1; ol<=n; ++ol) for(int zhas=1; zhas<=m; ++zhas) if(c[ol][zhas]=='1')ok=0;
if(ok)ans=max(ans,x*y);
}
}
cout<<ans<<endl;
}
int main() {
IShowSpeed;
int tt=1;
//cin>>tt;
while(tt--) solve();
}
