#include<bits/stdc++.h>
#define god dimasi5eks
#pragma GCC optimize("O3")
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mod 1000000007
#define dancila 3.14159265359
#define eps 1e-9
using namespace std;
typedef long long ll;
int add(int a, int b)
{
ll x = a+b;
if(x >= mod)
x -= mod;
if(x < 0)
x += mod;
return x;
}
ll mul(ll a, ll b)
{
return (a*b) % mod;
}
ll pw(ll a, ll b)
{
ll ans = 1;
while(b)
{
if(b & 1)
ans = (ans * a) % mod;
a = (a * a) % mod;
b >>= 1;
}
return ans;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long rand_seed()
{
long long a = rng();
return a;
}
char c[2600][2600];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, m;
cin >> n >> m;
for(int i = 1; i <= n; ++i)
cin >> (c[i] + 1);
int mnx = m, mny = n;
for(int i = 1; i <= n; ++i)
{
int str = 0;
for(int j = 1; j <= m; ++j)
{
if(c[i][j] == '1')
++str;
else
{
if(str)
mnx = min(mnx, str);
str = 0;
}
}
if(str)
mnx = min(mnx, str);
}
for(int j = 1; j <= m; ++j)
{
int str = 0;
for(int i = 1; i <= n; ++i)
{
if(c[i][j] == '1')
++str;
else
{
if(str)
mny = min(mny, str);
str = 0;
}
}
if(str)
mny = min(mny, str);
}
cout << mnx * mny << '\n';
return 0;
}
