#include <bits/stdc++.h>
//#include "grader.h"
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>*/
#define ll long long
#define ll1 long long
#define ull unsigned long long
#define dou long double
#define str string
#define vll vector<ll>
#define vi vector<int>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vbool vector<bool>
#define vstr vector<str>
#define vvll vector<vll>
#define pb push_back
#define pf push_front
#define endl "\n"
#define fr first
#define se second
// #define sortcmp(a) sort(a.begin(), a.end(), cmp)
#define sort(a) sort(a.begin(), a.end())
#define all(a) a.begin(), a.end()
#define reverse(a) reverse(a.begin(), a.end())
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define INF 1000000000000000000
#define ordered_set tree<pll, null_type, less<pll>, rb_tree_tag, tree_order_statistics_node_update>
using namespace std;
//using namespace __gnu_pbds;
mt19937 rng(1488);
ll randll(ll l, ll r){
return uniform_int_distribution<ll>(l, r)(rng);
}
/*vector<map<ll, vll>> s;
vll p;
ll find(ll v) {
if (p[v] == v) return v;
return p[v] = find(p[v]);
}
void unite(ll a, ll b) {
a = find(a);
b = find(b);
if (a == b) return;
if (s[a].size() < s[b].size()) {
p[a] = b;
for (auto i : s[a]) {
for (int j : i.se) {
s[b][i.fr].pb(j);
}
}
s[a].clear();
}
else {
p[b] = a;
for (auto i : s[b]) {
for (int j : i.se) {
s[a][i.fr].pb(j);
}
}
s[b].clear();
}
}
vll tree1, d;
void push(ll v, ll tl, ll tr) {
if (tl == tr) return;
tree1[v*2] += d[v];
tree1[v*2+1] += d[v];
d[v*2] += d[v];
d[v*2+1] += d[v];
d[v] = 0;
tree1[v] = tree1[v*2]+tree1[v*2+1];
}
void bt(ll v, ll tl, ll tr, vll& a) {
if (tl == tr) {
tree1[v] = a[tl];
return;
}
ll tm = (tl+tr)/2;
bt(v*2, tl, tm, a);
bt(v*2, tm+1, tr, a);
tree1[v] = tree1[v*2]+tree1[v*2+1];
}
ll get(ll l, ll r, ll v, ll tl, ll tr) {
if (l <= tl && tr <= r) return tree1[v];
if (tl > r || tr < l) return 0;
ll tm = (tl+tr)/2;
push(v, tl, tr);
return get(l, r, v*2, tl, tm)+get(l, r, v*2+1, tm+1, tr);
}
void update(ll l, ll r, ll val, ll v, ll tl, ll tr) {
if (l <= tl && tr <= r) {
tree1[v] += val;
d[v] += val;
push(v, tl, tr);
return;
}
if (tl > r || tr < l) return;
ll tm = (tl+tr)/2;
push(v, tl, tr);
update(l, r, val, v*2, tl, tm);
update(l, r, val, v*2+1, tm+1, tr);
tree1[v] = tree1[v*2]+tree1[v*2+1];
}*/
ll sum(ll x, ll y, ll x1, ll y1, vvll& p) {
x ++, y ++, x1 ++, y1 ++;
return p[x1][y1]-p[x1][y-1]-p[x-1][y1]+p[x-1][y-1];
}
int main() {
ll n, m;
cin >> n >> m;
vstr s(n);
vvll p(n+7, vll(m+7, 0));
for (int i = 0; i < n; i ++) {
cin >> s[i];
}
for (int i = 1; i <= n; i ++) {
for (int j = 1; j <= m; j ++) {
p[i][j] = p[i-1][j]+p[i][j-1]-p[i-1][j-1];
if (s[i-1][j-1] == '1') p[i][j] ++;
}
}
ll minly = INF, minlx = INF;
for (int i = 0; i < n; i ++) {
ll k = 0;
for (int j = 0; j < m; j ++) {
if (s[i][j] == '1') k ++;
else if (k > 0) {
/*ll l = i, r = n;
while (r-l > 1) {
ll x = (l+r)/2;
if (sum(i, j-k, x, j-1, p) == (x-i+1)*(j-1-(j-k)+1)) l = x;
else r = x;
}*/
if (k < minly) {
minly = k;
//minlx = l-i+1;
}
/*if (k == minly) {
minlx = min(minlx, l-i+1);
}*/
k = 0;
}
}
}
//cout << minlx << ' ' << minly << endl;
ll minly1 = INF, minlx1 = INF;
for (int j = 0; j < m; j ++) {
ll k = 0;
for (int i = 0; i < n; i ++) {
if (s[i][j] == '1') k ++;
else if (k > 0) {
/*ll l = j, r = m;
while (r-l > 1) {
ll x = (l+r)/2;
if (sum(i-k, j, i-1, x, p) == (x-j+1)*(i-(i-k))) l = x;
else r = x;
}*/
if (k < minlx1) {
minlx1 = k;
//minly1 = l-j+1;
}
/*if (k == minlx1) {
minly1 = min(minly1, l-j+1);
}*/
k = 0;
}
}
}
/*minly = min(minly, minly1);
minlx = min(minlx, minlx1);*/
cout << minly*minlx1 << endl;
}
