#include<bits/stdc++.h>
using namespace std;
#define IOS ios_base::sync_with_stdio(0); cin.tie(0);
#define int long long
#define pb push_back
#define fi first
#define se second
#define mp make_pair
const int mod = 1e9 + 7;
const int maxn = 2505;
int n, m;
char grid[maxn][maxn];
void solve(){
if(n == 1 || m == 1){
if(n == 1){
//vector<int> cnt;
int i = 1;
int mini = LLONG_MAX;
for(; i <= m; i++){
int tmp;
if(grid[1][i] == '1'){
tmp = 1;
while(grid[1][i + 1] == '1'){
tmp++;
i++;
}
}else{
continue;
}
//cnt.pb(tmp);
mini = min(mini, tmp);
}
cout << mini << endl;
}else{
int i = 1;
int mini = LLONG_MAX;
for(; i <= n; i++){
int tmp;
if(grid[i][1] == '1'){
tmp = 1;
while(grid[i + 1][1] == '1'){
tmp++;
i++;
}
}else{
continue;
}
//cnt.pb(tmp);
mini = min(mini, tmp);
}
cout << mini << endl;
}
return;
}else{
//cek tiap baris
int minsbaris = LLONG_MAX;
for(int i = 1; i <= n; i++){
int j = 1;
int mini = LLONG_MAX;
for(; j <= m; j++){
int tmp;
if(grid[i][j] == '1'){
tmp = 1;
while(grid[i][j + 1] == '1'){
tmp++;
j++;
}
}else{
continue;
}
mini = min(mini, tmp);
}
minsbaris = min(minsbaris, mini);
}
//cek tiap kolom
int minkolom = LLONG_MAX;
for(int i = 1; i <= m; i++){
int j = 1;
int mini = LLONG_MAX;
for(; j <= n; j++){
int tmp;
if(grid[j][i] == '1'){
tmp = 1;
while(grid[j + 1][i] == '1'){
tmp++;
j++;
}
}else{
continue;
}
mini = min(mini, tmp);
}
minkolom = min(minkolom, mini);
}
//cout << "minsbaris = " << minsbaris << " minkolom = " << minkolom << endl;
cout << minkolom * minsbaris << endl;
}
}
int32_t main()
{
IOS
cin >> n >> m;
string s[n + 1];
for(int i = 1; i <= n; i++){
cin >> s[i];
}
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
grid[i][j] = s[i][j - 1];
}
}
solve();
}
