#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define vt vector
#define f first
#define s second
#define all(x) (x).begin(), (x).end()
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, b) FOR(i, 0, b)
#define ROF(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define pb push_back
#define endl '\n'
#ifndef LOCAL
#define cerr if (0) std::cerr
#endif
/*
N^3: find max width for each given height
*/
int rs, cs;
vt<vt<bool>> grid;
main() {
cin.tie(0)->sync_with_stdio();
cin >> rs >> cs;
rs += 2, cs += 2;
grid.resize(rs, vt<bool>(cs));
FOR (r, 1, rs - 1) {
FOR (c, 1, cs - 1) {
char ch; cin >> ch;
grid[r][c] = ch - '0';
}
}
int mxw = cs, mxh = rs;
F0R (r, rs) {
int streak = 0;
F0R (c, cs) {
if (grid[r][c]) streak++;
else if (streak) mxw = min(mxw, streak), streak = 0;
}
}
F0R (c, cs) {
int streak = 0;
F0R (r, rs) {
if (grid[r][c]) streak++;
else if (streak) mxh = min(mxh, streak), streak = 0;
}
}
cout << mxw * mxh << endl;
}
