#include <iostream>
#include <assert.h>
#include <math.h>
#include <memory.h>
#include <stdio.h>
#include <algorithm>
#include <complex>
#include <ctime>
#include <fstream>
#include <iostream>
#include <list>
#include <queue>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <iomanip>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <array>
#include <random>
#include <chrono>
using namespace std;
#define CFp9rG6ig1PxX0Q7g2lto5mEq15 cin
#define QjnJgPLmGZ4lto5GnW7FSFF8OMMx1tnDAbw8NgrFU4 scanf
#define u9C2bzKGRRn2lto5CQfejT6jveVjJnPgue setfill
#define f6e5FPmaI2csETYIelto5sONx9a7bpOUvRb2x6IMw7 setw
#define Z9qe4On8Hg0XDKXKlL2hivHlto5rqX putchar
#define LF4kRwlto5Yk4Hv cout
#define iSPWpD7lto55qm rend
#define bBTQlto5B second
#define eFqlto5ChWNLEI0N2PJtUUyBlkdLLx49YjPE first
#define Mg8jWzpgz48Oq3lto5k1KzmoKbKQkJ2CO4Qyo2TmsBl begin
#define JdPOmCQA1fNmFcflto5l bool
#define VDmmBDpVRIXE7ihlto5ZWCqxDWKqdnxV rbegin
#define FR4t5gyx2lto5GAUqIDP7bsAXWWiM0z9w push_back
#define QN5jvmHsqZbQtr1y78Y1jvlto56flh3ZE4PukcpaJ7p88 operator
#define eciCju0L4W9m2ZW5YBlto5owzqKzCwnKFWPhFtsBU5grSUurq1P puts
#define LfNKlto5cjAyAk3Wdldx43Rlk length
#define f53XY4Nrtv6fsiPRGpEkLhzqfewyq6GWlto5JUlq8E84KqYVGqDYwp return
#define nd8SZ6j5Nhvb2hQml2sAtQv1Hlto504OK74OTZo1i end
#define qQrQUAihLlcmgT77dlto5ihAVrEk else
#define D1lto5L if
#define D4lto5VBPF7es9RAfc auto
#define HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY for
#define VAtpdBZ3LmVwCDibqQjxZlto53oaXZNCyLyYGN main
#define Hm4Wc1R3424xTqtSrY7rVHgzglto5WECkF90k6cLB5SD9 string
#define YC8rvhbleItdPo0VRkCDkMknBlUuqFlto5oiUge3HrhRKJ71J4txGyiwizyW getchar
#define sL0Dd8ZJn2tFJ9RwvuGBnE7koEWmlto5s6v5H long long
#define jszV6BNnkB67XcqYQWGd9kalto5osHj0qjj87grJVgyXn5uQXtiU printf
#define KFLlg2Fplto5g6zRrHZ8tv char
#define qs5ylto5zVg6pGvXVHEYnvlW2Jn freopen
#define tmflHyEcedODzX9OfGmBORAEMKlto5qYPKs3sFLPjoVmfZL vector
#define J27RpjH78mXWoNVfBM8lto5TyjEmFRSF4X void
#define H58aqsHCg5aWvlto52xHLq2 insert
#define chZH0sn5lto5fNxOoM7zppEoLb while
#define OYtDNxNQEm0FgoKxUlto5tJqhupZJVoYw0mTuRIQgcwVccCQNA const
#define int sL0Dd8ZJn2tFJ9RwvuGBnE7koEWmlto5s6v5H
#define lto5pulWN   HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY (int j=m-1; j>=0; --j) {
#define lto5nEk8SgSRZ5ptMryXTjc3LS73JwuY58nUo1      CFp9rG6ig1PxX0Q7g2lto5mEq15 >> a[i][j];
#define lto5JB5ukBGaxm1QBCN3zgfpntdcq4sgH   chZH0sn5lto5fNxOoM7zppEoLb (!st.empty()) st.pop();
#define lto5EQBtOZpnU0NHKS82UUYmtmiUvJn7wSMb        d2[j] = st.empty() ? m : st.top();
#define lto5RogIifS9atm3NEGgwYtHGqkY int n, m;
#define lto5NSl7lsJMw8NpJFsOLHN70wVhUKW             d[j] = i;
#define lto5uhaRlyU6BeH1keI HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY (int i=0; i<n; ++i)
#define lto5OUbO9pJkftZze1S         st.push (j);
#define lto58UlmvfCUL0xCVrBQgmK         st.push (j);
#define lto5vHOkUmcgzSWZ33NWw tmflHyEcedODzX9OfGmBORAEMKlto5qYPKs3sFLPjoVmfZL < tmflHyEcedODzX9OfGmBORAEMKlto5qYPKs3sFLPjoVmfZL<int> > a (n, tmflHyEcedODzX9OfGmBORAEMKlto5qYPKs3sFLPjoVmfZL<int> (m));
#define lto5yeCASMagY1NVvZvokvE8NDQ0cth6X       d1[j] = st.empty() ? -1 : st.top();
#define lto5cGxSiASlZOzTY5jY1h42A       chZH0sn5lto5fNxOoM7zppEoLb (!st.empty() && d[st.top()] <= d[j])  st.pop();
#define lto5P4pRKOkio   HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY (int j=0; j<m; ++j)
#define lto5lGZOmbep        D1lto5L (a[i][j] == 1)
#define lto5Pm3k7Jp8Jv5UbTiq1gFxxaPcphdO9um2 HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY (int i=0; i<n; ++i) {
#define lto5QOqdfcN178C2tT41b2Y0TBq23GNzUr  HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY (int j=0; j<m; ++j)
#define lto56hq0vxg1QxTEA1M9ZM  HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY (int j=0; j<m; ++j) {
#define lto5QKFF4TpsLc6ikW0ydsmPcC02aV9     chZH0sn5lto5fNxOoM7zppEoLb (!st.empty()) st.pop();
#define lto5tKoNLSDQU LF4kRwlto5Yk4Hv << ans;
#define lto5V81v8       ans = max (ans, (i - d[j]) * (d2[j] - d1[j] - 1));
#define lto5YwYU80LJDcOciVrZNwb5cSM8E       chZH0sn5lto5fNxOoM7zppEoLb (!st.empty() && d[st.top()] <= d[j])  st.pop();
#define lto5StuZHJBdy1GZ0pXYkRoDYHPnY }
#define lto5KJqN0J6orQzYJJYEzcuDIBa CFp9rG6ig1PxX0Q7g2lto5mEq15 >> n >> m;
#define lto5PbaDQ stack<int> st;
#define lto5YV7ngZat4sSDXUWxwEqjv4UzhnyeyYlV    HJsq9nHPBuUC66BKMlto56NhmzKG84gOgpYs7NeY (int j=0; j<m; ++j)
#define lto5ycpN2s  }
#define lto5hhZ1G4Q1uI0Q3jTHzlRdZoyxV6kpyL int ans = 0;
#define lto5bGSMPnIC2TaWHA  }
#define lto50dNDB8bzF4oP1UkbDBZHzxvuQQ }
#define lto5FVvGD1aEVIEmnp6xoupsT4 tmflHyEcedODzX9OfGmBORAEMKlto5qYPKs3sFLPjoVmfZL<int> d (m, -1), d1 (m), d2 (m);
#define lto5rtZiCTA1EvP2RQqk97WDpzAKBCo signed VAtpdBZ3LmVwCDibqQjxZlto53oaXZNCyLyYGN() {
lto5rtZiCTA1EvP2RQqk97WDpzAKBCo
lto5RogIifS9atm3NEGgwYtHGqkY
lto5KJqN0J6orQzYJJYEzcuDIBa
lto5vHOkUmcgzSWZ33NWw
lto5uhaRlyU6BeH1keI
lto5P4pRKOkio
lto5nEk8SgSRZ5ptMryXTjc3LS73JwuY58nUo1
lto5hhZ1G4Q1uI0Q3jTHzlRdZoyxV6kpyL
lto5FVvGD1aEVIEmnp6xoupsT4
lto5PbaDQ
lto5Pm3k7Jp8Jv5UbTiq1gFxxaPcphdO9um2
lto5QOqdfcN178C2tT41b2Y0TBq23GNzUr
lto5lGZOmbep
lto5NSl7lsJMw8NpJFsOLHN70wVhUKW
lto5QKFF4TpsLc6ikW0ydsmPcC02aV9
lto56hq0vxg1QxTEA1M9ZM
lto5cGxSiASlZOzTY5jY1h42A
lto5yeCASMagY1NVvZvokvE8NDQ0cth6X
lto58UlmvfCUL0xCVrBQgmK
lto5ycpN2s
lto5JB5ukBGaxm1QBCN3zgfpntdcq4sgH
lto5pulWN
lto5YwYU80LJDcOciVrZNwb5cSM8E
lto5EQBtOZpnU0NHKS82UUYmtmiUvJn7wSMb
lto5OUbO9pJkftZze1S
lto5bGSMPnIC2TaWHA
lto5YV7ngZat4sSDXUWxwEqjv4UzhnyeyYlV
lto5V81v8
lto50dNDB8bzF4oP1UkbDBZHzxvuQQ
lto5tKoNLSDQU
lto5StuZHJBdy1GZ0pXYkRoDYHPnY