#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
#define ll long long
#define rep(i,n,N) for(int i = n; i<=N; ++i)
#define rap(i,n,N) for(int i = n; i>=N; --i)
#define For(i,n,N) for(int i = n; i< N; ++i)
#define endl '\n'
const int MAX = 2500 + 5;
int n,m,mnr,mnc,cnt;
char c;
bool x[MAX][MAX];
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n>>m;
mnr = n, mnc = m;
rep(i,1,n){
rep(j,1,m){
cin>>c;
x[i][j] = c=='1';
if(x[i][j])++cnt;
else if(cnt)mnc = min(mnc, cnt), cnt = 0;
}
if(cnt)mnc = min(mnc, cnt), cnt = 0;
}
rep(j,1,m){
rep(i,1,n){
if(x[i][j])++cnt;
else if(cnt)mnr = min(mnr, cnt), cnt = 0;
}
if(cnt)mnr = min(mnr, cnt), cnt = 0;
}
cout<<mnr*mnc<<endl;
return 0;
}
