#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#define in(x) freopen(x,"r",stdin)
#define out(x) freopen(x,"w",stdout)
#define f first
#define s second
#define pb push_back
#define INF 1000000000
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const ll N = 3e3;
const ll oo = 1e10;
ll pr[N][N];
ll n, m;
ll sum(ll sx, ll sy, ll ex, ll ey)
{
return pr[ex][ey] - pr[sx - 1][ey] - pr[ex][sy - 1] + pr[sx - 1][sy - 1];
}
ll Check(ll width, ll x, ll y)
{
ll sy = y - width;
ll lx = 1, rx = x;
while (lx < rx)
{
ll mdl = (lx + rx) >> 1;
if (sum(mdl, sy, x, y) != (x - mdl + 1) * (width + 1)) lx = mdl + 1;
else rx = mdl;
}
ll sx = lx;
lx = x, rx = n;
while (lx < rx)
{
ll mdl = (lx + rx + 1) >> 1;
if (sum(x, sy, mdl, y) != (mdl - x + 1) * (width + 1)) rx = mdl - 1;
else lx = mdl;
}
ll ex = lx;
return ex - sx + 1;
}
int main()
{
ios_base::sync_with_stdio(0);
iostream::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
string a[n];
for (ll i = 0; i < n; i++) cin >> a[i];
for (ll i = 1; i <= n; i++)
for (ll j = 1; j <= m; j++) pr[i][j] = pr[i - 1][j] + pr[i][j - 1] - pr[i - 1][j - 1] + (a[i - 1][j - 1] == '1');
ll ansx = oo, ansy = oo;
for (ll i = 0; i < n; i++)
{
ll group = -oo;
if (a[i][0] == '1') group = 0;
for (ll j = 1; j < m; j++)
if (a[i][j] == '1')
{
if (a[i][j - 1] == '1') group++;
else group = 0;
}
else
{
if (group != -oo)
{
ll x = Check(group, i + 1, j);
ansx = min(ansx, group + 1);
ansy = min(ansy, x);
}
group = -oo;
}
if (group != -oo)
{
ll x = Check(group, i + 1, m);
ansx = min(ansx, group + 1);
ansy = min(ansy, x);
}
}
cout << ansx * ansy;
}
