#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e3 + 5;
int top[maxn][maxn], bot[maxn][maxn], at[maxn], w[maxn];
char a[maxn][maxn];
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++) cin >> a[i][j];
}
int mw = 1e9, mh = 1e9;
for(int j = 1; j <= m; j++){
for(int i = 1; i <= n; i++){
if(a[i][j] == '0') continue;
top[i][j] = top[i - 1][j] + 1;
}
for(int i = n; i >= 1; i--){
if(a[i][j] == '0') continue;
bot[i][j] = bot[i + 1][j] + 1;
}
for(int i = 1; i <= n; i++){
if(a[i][j] == '1') at[i]++;
else{
if(at[i]) mw = min(mw, at[i]);
at[i] = 0;
}
}
}
for(int i = 1; i <= n; i++) if(at[i]) mw = min(mw, at[i]);
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
if(a[i][j] == '1') mh = min(mh, top[i][j] + bot[i][j] - 1);
}
}
for(int i = 0; i <= mw; i++) w[i] = mh;
for(int i = 1; i <= n; i++){
int ln = 0, ma = 1e9, mb = 1e9;
for(int j = 1; j <= m; j++){
if(a[i][j] == '1'){
ma = min(ma, top[i][j]),
mb = min(mb, bot[i][j]);
ln++;
w[ln] = min(w[ln], ma + mb - 1);
}else ln = 0, ma = 1e9, mb = 1e9;
}
ln = 0, ma = 1e9, mb = 1e9;
for(int j = m; j >= 1; j--){
if(a[i][j] == '1'){
ma = min(ma, top[i][j]),
mb = min(mb, bot[i][j]);
ln++;
w[ln] = min(w[ln], ma + mb - 1);
}else ln = 0, ma = 1e9, mb = 1e9;
}
}
int ans = 0;
for(int i = 0; i <= mw; i++) ans = max(ans, i * w[i]);
cout << ans;
}
