#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define fi first
#define in inline
#define se second
#define mp make_pair
#define pb push_back
const int N = 210;

ll read(){
	ll x = 0,f = 1;char c = getchar();
	for(;c < '0' || c > '9';c = getchar())if(c == '-')f = -1;
	for(;c >= '0' && c <= '9';c = getchar())x = (x<<1) + (x<<3) + c-'0';
	return x * f;
}


int n,m;
ll a[N][N],ans;
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() + a[i-1][j] + a[i][j-1] - a[i-1][j-1];
	for(int i = 1;i <= n;i++){
		for(int j = 1;j <= m;j++){
			for(int k = i;k <= n;k++){
				for(int l = j;l <= m;l++)
					if(a[k][l] - a[i-1][l] - a[k][j-1] + a[i-1][j-1] >= 0)ans = max(ans,(ll)(k - i + 1) * (l - j + 1));
			}
		}
	}
	printf("%lld\n",ans);

	return 0;

}