/*
IN THE NAME OF GOD
*/
#include <bits/stdc++.h>
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef long double ld;
#define F first
#define S second
#define Mp make_pair
#define pb push_back
#define pf push_front
#define size(x) ((ll)x.size())
#define all(x) (x).begin(),(x).end()
#define kill(x) cout << x << '\n', exit(0);
#define fuck(x) cout << "(" << #x << " , " << x << ")" << endl
#define endl '\n'
const int N = 1e5+23, lg = 18;
ll Mod = 1e9+7; //998244353;
inline ll MOD(ll a, ll mod=Mod) {a%=mod; (a<0)&&(a+=mod); return a;}
inline ll poww(ll a, ll b, ll mod=Mod) {
ll ans = 1;
a=MOD(a, mod);
while (b) {
if (b & 1) ans = MOD(ans*a, mod);
b >>= 1;
a = MOD(a*a, mod);
}
return ans;
}
int n, m, h=1e9, w=1e9, mark[2505][2505], ml[2505][2505], mu[2505][2505];
int main () {
ios_base::sync_with_stdio(false), cin.tie(0);
cin>>n>>m; h=n, w=m;
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++) {
char c; cin>>c;
mark[i][j] = (c=='1');
}
}
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++) {
if(mark[i][j] == 0) continue;
mu[i][j] = ml[i][j] = 1;
if(mark[i-1][j]) mu[i][j] += mu[i-1][j];
if(mark[i][j-1]) ml[i][j] += mu[i][j-1];
if(mark[i+1][j] == 0) h = min(h, mu[i][j]);
if(mark[i][j+1] == 0) w = min(w, ml[i][j]);
}
}
cout<<h*w<<endl;
return 0;
}
