#include <bits/stdc++.h>
using namespace std;
int dpHorizontal[2505][2505] = {0};
int dpVertical[2505][2505] = {0};
int main()
{
int n, m;
cin >> n >> m;
char arr[n + 5][m + 5];
for(int i = 0; i < n; i++)
{
for(int j = 0; j < m; j++)
{
cin >> arr[i][j];
}
}
int res = 0;
int sum = 0;
if(n == 1 || m == 1)
{
if(n == 1)
{
for(int i = 0; i < m; i++)
{
// cout << res << " ";
if(arr[0][i] == '1')
{
sum++;
}
else
{
if(res == 0)res = sum;
else if(res > 0 && sum > 0)
{
res = min(res, sum);
}
sum = 0;
}
}
if(res == 0)res = sum;
else if(res > 0 && sum > 0) res = min(res, sum);
}
else if(m == 1)
{
for(int i = 0; i < n; i++)
{
// cout << sum << " ";
if(arr[i][0] == '1')
{
sum++;
}
else
{
if(res == 0)res = sum;
else if(res > 0 && sum > 0)
{
res = min(res, sum);
}
sum = 0;
}
}
if(res == 0)res = sum;
else if(res > 0 && sum > 0)res = min(res, sum);
}
}
else
{
for(int i = 1; i <= n; i++)
{
for(int j = 1; j <= m; j++)
{
if(arr[i - 1][j - 1] == '1')
{
dpHorizontal[i][j] = dpHorizontal[i][j - 1] + 1;
}
}
}
for(int i = 1; i <= m; i++)
{
for(int j = 1; j <= n; j++)
{
if(arr[j - 1][i - 1] == '1')
{
dpVertical[j][i] = dpVertical[j - 1][i] + 1;
}
}
}
// for(int i = 0; i <= n; i++)
// {
// for(int j = 0; j <= m; j++)
// {
// cout << dpVertical[i][j] << " ";
// }
// cout << endl;
// }
int minHorizontal = -1;
for(int i = 1; i <= n; i++)
{
for(int j = 1; j <= m; j++)
{
if(dpHorizontal[i][j + 1] == 0 && dpHorizontal[i][j] > 0)
{
if(minHorizontal == -1)
{
minHorizontal = dpHorizontal[i][j];
}
else minHorizontal = min(minHorizontal, dpHorizontal[i][j]);
}
}
}
// cout << minHorizontal << endl;
int minVertical = -1;
for(int i = 1; i <= m; i++)
{
for(int j = 1; j <= n; j++)
{
if(dpVertical[j + 1][i] == 0 && dpVertical[j][i] > 0)
{
if(minVertical == -1)
{
minVertical = dpVertical[j][i];
}
else minVertical= min(minVertical, dpVertical[j][i]);
}
}
}
res = minHorizontal * minVertical;
}
cout << res << endl;
return 0;
}
