#include<bits/stdc++.h>
using namespace std;
#define ll long long
inline ll read(){
    ll x=0,f=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){
        if(ch=='-')f=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9'){
        x=x*10+ch-'0';
        ch=getchar(); 
    }
    return x*f;
}
ll n,m,ans;
ll s[210][210],a[210][210];
int main(){
    freopen("long.in","r",stdin);
    freopen("long.out","w",stdout);
    n=read(),m=read();
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            a[i][j]=read();
            s[i][j]=s[i-1][j]+s[i][j-1]-s[i-1][j-1]+a[i][j];
            for(int x=0;x<i;x++){
                for(int y=0;y<j;y++){
                    if(s[i][j]-s[x][j]-s[i][y]+s[x][y]>0)ans=max(ans,(ll)(i-x)*(j-y));
                }
            }
        }
    }
    cout<<ans;
    return 0;
}