#include <bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define ff first
#define ss second
const int inf = 4e18;
const int mod = 1e9+7;
using namespace std;
int exp(int x,int a)
{
int res = 1;
for(;a>0;res=(a%2?res*x%mod:res),x=x*x%mod,a/=2);
return res;
}
int inv(int x)
{
return exp(x,mod-2);
}
void solve()
{
int n,m;
cin >> n >> m;
vector<string> g(n);
for(auto&s:g)cin>>s;
int ans = 1;
int mini = m;
for(int i = 0; i < n; i++)
{
int prev = 0;
for(int j = 0;j < m; j++)
if(j>0&&g[i][j]!=g[i][j-1])
{
if(g[i][j]=='0')
mini = min(mini,j-prev);
prev = j;
}
if(g[i][m-1]=='1')
mini = min(mini,m-prev);
}
ans*=mini;
mini = n;
for(int j = 0;j < m;j++)
{
int prev = 0;
for(int i = 0; i < n; i++)
if(i>0&&g[i][j]!=g[i-1][j])
{
if(g[i][j]=='0')
mini = min(mini,i-prev);
prev = i;
}
if(g[n-1][j]=='1')
mini = min(mini,n-prev);
}
cout<<ans*mini<<'\n';
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while(t--)
solve();
}
