// In the Name of God
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define ld long double
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define sz(a) int(a.size())
#define all(v) v.begin(), v.end()
#define bpc(v) __builtin_popcountll(v)
#define itr iterator
#define rep(i, a, b) for (int i = a; i <= b; ++i)
#define per(i, a, b) for (int i = a; i >= b; --i)
#define ub upper_bound
#define lb lower_bound
const int N = 25e2 + 5;
const int mod = 1e8 + 7;
const int inf = 1e9 + 1;
const double eps = 1e-15;
const int pw = 257;
int n, m, last[N], cnt, x, y;
string s;
int main() {
#ifdef Madi
freopen(".in", "r", stdin);
freopen(".out", "w", stdout);
#endif
ios_base :: sync_with_stdio(false); cin.tie(NULL);
cin >> n >> m;
x = m, y = n;
rep(i, 1, n) {
cin >> s;
cnt = 0;
rep(j, 0, m - 1) {
if (s[j] == '0') {
if (cnt)
x = min(x, cnt);
cnt = 0;
if (last[j] != i - 1)
y = min(y, i - last[j] - 1);
last[j] = i;
}
else
++cnt;
}
if (cnt)
x = min(x, cnt);
}
rep(j, 0, m - 1)
if (last[j] != n)
y = min(y, n + 1 - last[j] - 1);
cout << x * y;
#ifdef Madi
cerr << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
return 0;
}
